Instruction and logic for parallel multi-step power management flow

ABSTRACT

A parallel multi-step power management flow apparatus and method for using the same are disclosed. In one embodiment, an integrated circuit comprises a plurality of processing entities to execute operations, a power controller coupled to the plurality of processing entities to control power management for the plurality of processing entities, and a plurality of agents, where each of the plurality of agents is operable to perform a power control flow for one of the processing entities by separately scheduling, using a scheduler, and executing a plurality of power control flow phases in response to a plurality of requests received from the power controller, and each agent is operable to send a plurality of acknowledgements, one acknowledgement for each phase, upon completion of the plurality of power control flow phases.

FIELD OF THE INVENTION

The present disclosure pertains to the field of processing logic,microprocessors, and associated instruction set architecture that, whenexecuted by the processor or other processing logic, perform logical,mathematical, or other functional operations.

DESCRIPTION OF RELATED ART

Power management is used in electrical devices, such as, for example, aprocessor, a system-on-chip (SoCs) and other integrated circuits, toreduce power consumption. The reduction in power is typically done byturning off or placing all or portions of a device in a lower powerstate when it's less active or inactive. That is, when nothing useful isbeing performed, various parts of the device can be powered down to saveenergy.

Some devices have various power management states. For example, someprocessors have multiple idle states, referred to as C-states. In oneimplementation, there are six C-states, namely C0-C6, where C0 is anactive state with full power and performance, and C6 is a deep sleepstate in which power is shut off to the entire processor and processorstate is saved in a small memory.

In order to enter one of the reduced power consumption states, in oneimplementation, a power control unit (PCU), or P-unit, proceeds througha number of phases of a finite state machine (FSM) and communicatesevery phase of the power management flow serially to the core orintellectual property (IP) units being managed. The PCU waits until thecore has completed executing each phase before starting a new phase.After each phase is completed, the core sends an acknowledgementindicating that the power phase has been completed. In response to theacknowledgement, the PCU starts sending communications for the nextphase. The back and forth communication that proceeds serially betweenthe PCU and the core as phases are performed has high performance cost.

DESCRIPTION OF THE FIGURES

Embodiments are illustrated by way of example and not limitation in theFigures of the accompanying drawings:

FIG. 1A is a block diagram of a system according to one embodiment;

FIG. 1B is a block diagram of a system according to one embodiment;

FIG. 1C is a block diagram of a system according to one embodiment;

FIG. 2 is a block diagram of a processor according to one embodiment;

FIG. 3A illustrates packed data types according to one embodiment;

FIG. 3B illustrates packed data types according one embodiment;

FIG. 3C illustrates packed data types according to one embodiment;

FIG. 3D illustrates an instruction encoding according to one embodiment;

FIG. 3E illustrates an instruction encoding according to one embodiment;

FIG. 3F illustrates an instruction encoding according to one embodiment;

FIG. 4A illustrates elements of a processor micro-architecture accordingto one embodiment;

FIG. 4B illustrates elements of a processor micro-architecture accordingto one embodiment;

FIG. 5 is a block diagram of a processor according to one embodiment;

FIG. 6 is a block diagram of a computer system according to oneembodiment;

FIG. 7 is a block diagram of a computer system according to oneembodiment;

FIG. 8 is a block diagram of a computer system according to oneembodiment;

FIG. 9 is a block diagram of a system-on-a-chip according to oneembodiment;

FIG. 10 is a block diagram of a processor according to one embodiment;

FIG. 11 is a block diagram of an IP core development system according toone embodiment;

FIG. 12 illustrates an architecture emulation system according to oneembodiment.

FIG. 13 illustrates a system to translate instructions according to oneembodiment.

FIG. 14 is a block diagram of a processor in accordance with anembodiment.

FIG. 15 illustrates one embodiment of supplying power to a core.

FIG. 16 illustrates one embodiment of the clock gating of the clocksignal of the core.

FIG. 17 illustrates one embodiment of the five FSM phases.

FIG. 18 is a flow diagram of one embodiment of a FSM process to placethe core in a quiesced state.

FIG. 19 is a flow diagram of one embodiment of a FSM process to blockone or more interfaces to the core.

FIG. 20 is a flow diagram of one embodiment of a FSM process to stopclocking of the core.

FIG. 21 is a flow diagram of one embodiment of a FSM process to exit areduced power consumption state.

FIG. 22 is a flow diagram of one embodiment of a FSM process to causethe core to resume executing instructions.

FIG. 23 illustrates the sending of five requests, one for each phase, ofone embodiment of the power down flow in parallel as part of onemessage.

DETAILED DESCRIPTION

A multiphase power control flow and method for performing the same aredescribed. In one embodiment, the power control flow is a flow forplacing part of a device, such as, for example, an integrated circuit(e.g., a processor, system-on-chip (SoC), etc.) into a sleep state. Thepart of the device may be, for example, a core, controller, processingunit, or intellectual property (IP) block. In one embodiment, the sleepstate is a deep sleep state (e.g., a C6 C-state). In another embodiment,the power control flow is a flow for performing dynamic voltage andfrequency scaling (DVFS) with respect to a component.

In one embodiment, processing logic performs the power control flowwithin or in association with a processor, computer system, or otherprocessing apparatus. In the following description, numerous specificdetails such as processing logic, processor types, micro-architecturalconditions, events, enablement mechanisms, and the like are set forth inorder to provide a more thorough understanding of embodiments of thepresent invention. It will be appreciated, however, by one skilled inthe art that the invention may be practiced without such specificdetails. Additionally, some well known structures, circuits, and thelike have not been shown in detail to avoid unnecessarily obscuringembodiments of the present invention.

Although the following embodiments are described with reference to aprocessor, other embodiments are applicable to other types of integratedcircuits and logic devices. Similar techniques and teachings ofembodiments of the present invention can be applied to other types ofcircuits or semiconductor devices that can benefit from higher pipelinethroughput and improved performance. The teachings of embodiments of thepresent invention are applicable to any processor or machine thatperforms data manipulations. However, the present invention is notlimited to processors or machines that perform 512 bit, 256 bit, 128bit, 64 bit, 32 bit, or 16 bit data operations and can be applied to anyprocessor and machine in which manipulation or management of data isperformed. In addition, the following description provides examples, andthe accompanying drawings show various examples for the purposes ofillustration. However, these examples should not be construed in alimiting sense as they are merely intended to provide examples ofembodiments of the present invention rather than to provide anexhaustive list of all possible implementations of embodiments of thepresent invention.

Although the below examples describe instruction handling anddistribution in the context of execution units and logic circuits, otherembodiments of the present invention can be accomplished by way of adata or instructions stored on a machine-readable, tangible medium,which when performed by a machine cause the machine to perform functionsconsistent with at least one embodiment of the invention. In oneembodiment, functions associated with embodiments of the presentinvention are embodied in machine-executable instructions. Theinstructions can be used to cause a general-purpose or special-purposeprocessor that is programmed with the instructions to perform the stepsof the present invention. Embodiments of the present invention may beprovided as a computer program product or software which may include amachine or computer-readable medium having stored thereon instructionswhich may be used to program a computer (or other electronic devices) toperform one or more operations according to embodiments of the presentinvention. Alternatively, steps of embodiments of the present inventionmight be performed by specific hardware components that containfixed-function logic for performing the steps, or by any combination ofprogrammed computer components and fixed-function hardware components.

Instructions used to program logic to perform embodiments of theinvention can be stored within a memory in the system, such as DRAM,cache, flash memory, or other storage. Furthermore, the instructions canbe distributed via a network or by way of other computer readable media.Thus a machine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer), but is not limited to, floppy diskettes, optical disks,Compact Disc, Read-Only Memory (CD-ROMs), and magneto-optical disks,Read-Only Memory (ROMs), Random Access Memory (RAM), ErasableProgrammable Read-Only Memory (EPROM), Electrically ErasableProgrammable Read-Only Memory (EEPROM), magnetic or optical cards, flashmemory, or a tangible, machine-readable storage used in the transmissionof information over the Internet via electrical, optical, acoustical orother forms of propagated signals (e.g., carrier waves, infraredsignals, digital signals, etc.). Accordingly, the computer-readablemedium includes any type of tangible machine-readable medium suitablefor storing or transmitting electronic instructions or information in aform readable by a machine (e.g., a computer).

A design may go through various stages, from creation to simulation tofabrication. Data representing a design may represent the design in anumber of manners. First, as is useful in simulations, the hardware maybe represented using a hardware description language or anotherfunctional description language. Additionally, a circuit level modelwith logic and/or transistor gates may be produced at some stages of thedesign process. Furthermore, most designs, at some stage, reach a levelof data representing the physical placement of various devices in thehardware model. In the case where conventional semiconductor fabricationtechniques are used, the data representing the hardware model may be thedata specifying the presence or absence of various features on differentmask layers for masks used to produce the integrated circuit. In anyrepresentation of the design, the data may be stored in any form of amachine readable medium. A memory or a magnetic or optical storage suchas a disc may be the machine readable medium to store informationtransmitted via optical or electrical wave modulated or otherwisegenerated to transmit such information. When an electrical carrier waveindicating or carrying the code or design is transmitted, to the extentthat copying, buffering, or re-transmission of the electrical signal isperformed, a new copy is made. Thus, a communication provider or anetwork provider may store on a tangible, machine-readable medium, atleast temporarily, an article, such as information encoded into acarrier wave, embodying techniques of embodiments of the presentinvention.

In modern processors, a number of different execution units are used toprocess and execute a variety of code and instructions. Not allinstructions are created equal as some are quicker to complete whileothers can take a number of clock cycles to complete. The faster thethroughput of instructions, the better the overall performance of theprocessor. Thus it would be advantageous to have as many instructionsexecute as fast as possible. However, there are certain instructionsthat have greater complexity and require more in terms of execution timeand processor resources. For example, there are floating pointinstructions, load/store operations, data moves, etc.

As more computer systems are used in internet, text, and multimediaapplications, additional processor support has been introduced overtime. In one embodiment, an instruction set may be associated with oneor more computer architectures, including data types, instructions,register architecture, addressing modes, memory architecture, interruptand exception handling, and external input and output (I/O).

In one embodiment, the instruction set architecture (ISA) may beimplemented by one or more micro-architectures, which includes processorlogic and circuits used to implement one or more instruction sets.Accordingly, processors with different micro-architectures can share atleast a portion of a common instruction set. For example, Intel® Pentium4 processors, Intel® Core™ processors, and processors from AdvancedMicro Devices, Inc. of Sunnyvale CA implement nearly identical versionsof the x86 instruction set (with some extensions that have been addedwith newer versions), but have different internal designs. Similarly,processors designed by other processor development companies, such asARM Holdings, Ltd., MIPS, or their licensees or adopters, may share atleast a portion a common instruction set, but may include differentprocessor designs. For example, the same register architecture of theISA may be implemented in different ways in differentmicro-architectures using new or well-known techniques, includingdedicated physical registers, one or more dynamically allocated physicalregisters using a register renaming mechanism (e.g., the use of aRegister Alias Table (RAT), a Reorder Buffer (ROB) and a retirementregister file. In one embodiment, registers may include one or moreregisters, register architectures, register files, or other registersets that may or may not be addressable by a software programmer.

In one embodiment, an instruction may include one or more instructionformats. In one embodiment, an instruction format may indicate variousfields (number of bits, location of bits, etc.) to specify, among otherthings, the operation to be performed and the operand(s) on which thatoperation is to be performed. Some instruction formats may be furtherbroken defined by instruction templates (or sub formats). For example,the instruction templates of a given instruction format may be definedto have different subsets of the instruction format's fields and/ordefined to have a given field interpreted differently. In oneembodiment, an instruction is expressed using an instruction format(and, if defined, in a given one of the instruction templates of thatinstruction format) and specifies or indicates the operation and theoperands upon which the operation will operate.

Scientific, financial, auto-vectorized general purpose, RMS(recognition, mining, and synthesis), and visual and multimediaapplications (e.g., 2D/3D graphics, image processing, videocompression/decompression, voice recognition algorithms and audiomanipulation) may require the same operation to be performed on a largenumber of data items. In one embodiment, Single Instruction MultipleData (SIMD) refers to a type of instruction that causes a processor toperform an operation on multiple data elements. SIMD technology may beused in processors that can logically divide the bits in a register intoa number of fixed-sized or variable-sized data elements, each of whichrepresents a separate value. For example, in one embodiment, the bits ina 64-bit register may be organized as a source operand containing fourseparate 16-bit data elements, each of which represents a separate16-bit value. This type of data may be referred to as ‘packed’ data typeor ‘vector’ data type, and operands of this data type are referred to aspacked data operands or vector operands. In one embodiment, a packeddata item or vector may be a sequence of packed data elements storedwithin a single register, and a packed data operand or a vector operandmay a source or destination operand of a SIMD instruction (or ‘packeddata instruction’ or a ‘vector instruction’). In one embodiment, a SIMDinstruction specifies a single vector operation to be performed on twosource vector operands to generate a destination vector operand (alsoreferred to as a result vector operand) of the same or different size,with the same or different number of data elements, and in the same ordifferent data element order.

SIMD technology, such as that employed by the Intel® Core™ processorshaving an instruction set including x86, MMX™, Streaming SIMD Extensions(SSE), SSE2, SSE3, SSE4.1, and SSE4.2 instructions, ARM processors, suchas the ARM Cortex® family of processors having an instruction setincluding the Vector Floating Point (VFP) and/or NEON instructions, andMIPS processors, such as the Loongson family of processors developed bythe Institute of Computing Technology (ICT) of the Chinese Academy ofSciences, has enabled a significant improvement in applicationperformance (Core™ and MMX™ are registered trademarks or trademarks ofIntel Corporation of Santa Clara, Calif.).

In one embodiment, destination and source registers/data are genericterms to represent the source and destination of the corresponding dataor operation. In some embodiments, they may be implemented by registers,memory, or other storage areas having other names or functions thanthose depicted. For example, in one embodiment, “DEST1 ” may be atemporary storage register or other storage area, whereas “SRC1 ” and“SRC2 ” may be a first and second source storage register or otherstorage area, and so forth. In other embodiments, two or more of the SRCand DEST storage areas may correspond to different data storage elementswithin the same storage area (e.g., a SIMD register). In one embodiment,one of the source registers may also act as a destination register by,for example, writing back the result of an operation performed on thefirst and second source data to one of the two source registers servingas a destination registers.

FIG. 1A is a block diagram of an exemplary computer system formed with aprocessor that includes execution units to execute an instruction inaccordance with one embodiment of the present invention. System 100includes a component, such as a processor 102 to employ execution unitsincluding logic to perform algorithms for process data, in accordancewith the present invention, such as in the embodiment described herein.System 100 is representative of processing systems based on the PENTIUM®III, PENTIUM® 4, Xeon™, Itanium®, XScale™ and/or StrongARM™microprocessors available from Intel Corporation of Santa Clara,California, although other systems (including PCs having othermicroprocessors, engineering workstations, set-top boxes and the like)may also be used. In one embodiment, sample system 100 may execute aversion of the WINDOWS™ operating system available from MicrosoftCorporation of Redmond, Wash., although other operating systems (UNIXand Linux for example), embedded software, and/or graphical userinterfaces, may also be used. Thus, embodiments of the present inventionare not limited to any specific combination of hardware circuitry andsoftware.

Embodiments are not limited to computer systems. Alternative embodimentsof the present invention can be used in other devices such as handhelddevices and embedded applications. Some examples of handheld devicesinclude cellular phones, Internet Protocol devices, digital cameras,personal digital assistants (PDAs), and handheld PCs. Embeddedapplications can include a micro controller, a digital signal processor(DSP), system on a chip, network computers (NetPC), set-top boxes,network hubs, wide area network (WAN) switches, or any other system thatcan perform one or more instructions in accordance with at least oneembodiment.

FIG. 1A is a block diagram of a computer system 100 formed with aprocessor 102 that includes one or more execution units 108 to performan algorithm to perform at least one instruction in accordance with oneembodiment of the present invention. One embodiment may be described inthe context of a single processor desktop or server system, butalternative embodiments can be included in a multiprocessor system.System 100 is an example of a ‘hub’ system architecture. The computersystem 100 includes a processor 102 to process data signals. Theprocessor 102 can be a complex instruction set computer (CISC)microprocessor, a reduced instruction set computing (RISC)microprocessor, a very long instruction word (VLIW) microprocessor, aprocessor implementing a combination of instruction sets, or any otherprocessor device, such as a digital signal processor, for example. Theprocessor 102 is coupled to a processor bus 110 that can transmit datasignals between the processor 102 and other components in the system100. The elements of system 100 perform their conventional functionsthat are well known to those familiar with the art.

In one embodiment, the processor 102 includes a Level 1 (L1) internalcache memory 104. Depending on the architecture, the processor 102 canhave a single internal cache or multiple levels of internal cache.Alternatively, in another embodiment, the cache memory can resideexternal to the processor 102. Other embodiments can also include acombination of both internal and external caches depending on theparticular implementation and needs. Register file 106 can storedifferent types of data in various registers including integerregisters, floating point registers, status registers, and instructionpointer register.

Execution unit 108, including logic to perform integer and floatingpoint operations, also resides in the processor 102. The processor 102also includes a microcode (ucode) ROM that stores microcode for certainmacroinstructions. For one embodiment, execution unit 108 includes logicto handle a packed instruction set 109. By including the packedinstruction set 109 in the instruction set of a general-purposeprocessor 102, along with associated circuitry to execute theinstructions, the operations used by many multimedia applications may beperformed using packed data in a general-purpose processor 102. Thus,many multimedia applications can be accelerated and executed moreefficiently by using the full width of a processor's data bus forperforming operations on packed data. This can eliminate the need totransfer smaller units of data across the processor's data bus toperform one or more operations one data element at a time.

Alternate embodiments of an execution unit 108 can also be used in microcontrollers, embedded processors, graphics devices, DSPs, and othertypes of logic circuits. System 100 includes a memory 120. Memory 120can be a dynamic random access memory (DRAM) device, a static randomaccess memory (SRAM) device, flash memory device, or other memorydevice. Memory 120 can store instructions and/or data represented bydata signals that can be executed by the processor 102.

A system logic chip 116 is coupled to the processor bus 110 and memory120. The system logic chip 116 in the illustrated embodiment is a memorycontroller hub (MCH). The processor 102 can communicate to the MCH 116via a processor bus 110. The MCH 116 provides a high bandwidth memorypath 118 to memory 120 for instruction and data storage and for storageof graphics commands, data and textures. The MCH 116 is to direct datasignals between the processor 102, memory 120, and other components inthe system 100 and to bridge the data signals between processor bus 110,memory 120, and system I/O 122. In some embodiments, the system logicchip 116 can provide a graphics port for coupling to a graphicscontroller 112. The MCH 116 is coupled to memory 120 through a memoryinterface 118. The graphics card 112 is coupled to the MCH 116 throughan Accelerated Graphics Port (AGP) interconnect 114.

System 100 uses a proprietary hub interface bus 122 to couple the MCH116 to the I/O controller hub (ICH) 130. The ICH 130 provides directconnections to some I/O devices via a local I/O bus. The local I/O busis a high-speed I/O bus for connecting peripherals to the memory 120,chipset, and processor 102. Some examples are the audio controller,firmware hub (flash BIOS) 128, wireless transceiver 126, data storage124, legacy I/O controller containing user input and keyboardinterfaces, a serial expansion port such as Universal Serial Bus (USB),and a network controller 134. The data storage device 124 can comprise ahard disk drive, a floppy disk drive, a CD-ROM device, a flash memorydevice, or other mass storage device.

For another embodiment of a system, an instruction in accordance withone embodiment can be used with a system on a chip. One embodiment of asystem on a chip comprises of a processor and a memory. The memory forone such system is a flash memory. The flash memory can be located onthe same die as the processor and other system components. Additionally,other logic blocks such as a memory controller or graphics controllercan also be located on a system on a chip.

FIG. 1B illustrates a data processing system 140 which implements theprinciples of one embodiment of the present invention. It will bereadily appreciated by one of skill in the art that the embodimentsdescribed herein can be used with alternative processing systems withoutdeparture from the scope of embodiments of the invention.

Computer system 140 comprises a processing core 159 capable ofperforming at least one instruction in accordance with one embodiment.For one embodiment, processing core 159 represents a processing unit ofany type of architecture, including but not limited to a CISC, a RISC ora VLIW type architecture. Processing core 159 may also be suitable formanufacture in one or more process technologies and by being representedon a machine readable media in sufficient detail, may be suitable tofacilitate said manufacture.

Processing core 159 comprises an execution unit 142, a set of registerfile(s) 145, and a decoder 144. Processing core 159 also includesadditional circuitry (not shown) which is not necessary to theunderstanding of embodiments of the present invention. Execution unit142 is used for executing instructions received by processing core 159.In addition to performing typical processor instructions, execution unit142 can perform instructions in packed instruction set 143 forperforming operations on packed data formats. Packed instruction set 143includes instructions for performing embodiments of the invention andother packed instructions. Execution unit 142 is coupled to registerfile 145 by an internal bus. Register file 145 represents a storage areaon processing core 159 for storing information, including data. Aspreviously mentioned, it is understood that the storage area used forstoring the packed data is not critical. Execution unit 142 is coupledto decoder 144. Decoder 144 is used for decoding instructions receivedby processing core 159 into control signals and/or microcode entrypoints. In response to these control signals and/or microcode entrypoints, execution unit 142 performs the appropriate operations. In oneembodiment, the decoder is used to interpret the opcode of theinstruction, which will indicate what operation should be performed onthe corresponding data indicated within the instruction.

Processing core 159 is coupled with bus 141 for communicating withvarious other system devices, which may include but are not limited to,for example, synchronous dynamic random access memory (SDRAM) control146, static random access memory (SRAM) control 147, burst flash memoryinterface 148, personal computer memory card international association(PCMCIA)/compact flash (CF) card control 149, liquid crystal display(LCD) control 150, direct memory access (DMA) controller 151, andalternative bus master interface 152. In one embodiment, data processingsystem 140 may also comprise an I/O bridge 154 for communicating withvarious I/O devices via an I/O bus 153. Such I/O devices may include butare not limited to, for example, universal asynchronousreceiver/transmitter (UART) 155, universal serial bus (USB) 156,Bluetooth wireless UART 157 and I/O expansion interface 158.

One embodiment of data processing system 140 provides for mobile,network and/or wireless communications and a processing core 159 capableof performing SIMD operations including a text string comparisonoperation. Processing core 159 may be programmed with various audio,video, imaging and communications algorithms including discretetransformations such as a Walsh-Hadamard transform, a fast Fouriertransform (FFT), a discrete cosine transform (DCT), and their respectiveinverse transforms; compression/decompression techniques such as colorspace transformation, video encode motion estimation or video decodemotion compensation; and modulation/demodulation (MODEM) functions suchas pulse coded modulation (PCM).

FIG. 1C illustrates yet alternative embodiments of a data processingsystem capable of performing SIMD text string comparison operations. Inaccordance with one alternative embodiment, data processing system 160may include a main processor 166, a SIMD coprocessor 161, a cache memory167, and an input/output system 168. The input/output system 168 mayoptionally be coupled to a wireless interface 169. SIMD coprocessor 161is capable of performing operations including instructions in accordancewith one embodiment. Processing core 170 may be suitable for manufacturein one or more process technologies and by being represented on amachine readable media in sufficient detail, may be suitable tofacilitate the manufacture of all or part of data processing system 160including processing core 170.

For one embodiment, SIMD coprocessor 161 comprises an execution unit 162and a set of register file(s) 164. One embodiment of main processor 165comprises a decoder 165 to recognize instructions of instruction set 163including instructions in accordance with one embodiment for executionby execution unit 162. For alternative embodiments, SIMD coprocessor 161also comprises at least part of decoder 165B to decode instructions ofinstruction set 163. Processing core 170 also includes additionalcircuitry (not shown) which is not necessary to the understanding ofembodiments of the present invention.

In operation, the main processor 166 executes a stream of dataprocessing instructions that control data processing operations of ageneral type including interactions with the cache memory 167, and theinput/output system 168. Embedded within the stream of data processinginstructions are SIMD coprocessor instructions. The decoder 165 of mainprocessor 166 recognizes these SIMD coprocessor instructions as being ofa type that should be executed by an attached SIMD coprocessor 161.Accordingly, the main processor 166 issues these SIMD coprocessorinstructions (or control signals representing SIMD coprocessorinstructions) on the coprocessor bus 166 where from they are received byany attached SIMD coprocessors. In this case, the SIMD coprocessor 161will accept and execute any received SIMD coprocessor instructionsintended for it.

Data may be received via wireless interface 169 for processing by theSIMD coprocessor instructions. For one example, voice communication maybe received in the form of a digital signal, which may be processed bythe SIMD coprocessor instructions to regenerate digital audio samplesrepresentative of the voice communications. For another example,compressed audio and/or video may be received in the form of a digitalbit stream, which may be processed by the SIMD coprocessor instructionsto regenerate digital audio samples and/or motion video frames. For oneembodiment of processing core 170, main processor 166, and a SIMDcoprocessor 161 are integrated into a single processing core 170comprising an execution unit 162, a set of register file(s) 164, and adecoder 165 to recognize instructions of instruction set 163 includinginstructions in accordance with one embodiment.

FIG. 2 is a block diagram of the micro-architecture for a processor 200that includes logic circuits to perform instructions in accordance withone embodiment of the present invention. In some embodiments, aninstruction in accordance with one embodiment can be implemented tooperate on data elements having sizes of byte, word, doubleword,quadword, etc., as well as datatypes, such as single and doubleprecision integer and floating point datatypes. In one embodiment thein-order front end 201 is the part of the processor 200 that fetchesinstructions to be executed and prepares them to be used later in theprocessor pipeline. The front end 201 may include several units. In oneembodiment, the instruction prefetcher 226 fetches instructions frommemory and feeds them to an instruction decoder 228 which in turndecodes or interprets them. For example, in one embodiment, the decoderdecodes a received instruction into one or more operations called“micro-instructions” or “micro-operations” (also called micro op oruops) that the machine can execute. In other embodiments, the decoderparses the instruction into an opcode and corresponding data and controlfields that are used by the micro-architecture to perform operations inaccordance with one embodiment. In one embodiment, the trace cache 230takes decoded uops and assembles them into program ordered sequences ortraces in the uop queue 234 for execution. When the trace cache 230encounters a complex instruction, the microcode ROM 232 provides theuops needed to complete the operation.

Some instructions are converted into a single micro-op, whereas othersneed several micro-ops to complete the full operation. In oneembodiment, if more than four micro-ops are needed to complete ainstruction, the decoder 228 accesses the microcode ROM 232 to do theinstruction. For one embodiment, an instruction can be decoded into asmall number of micro ops for processing at the instruction decoder 228.In another embodiment, an instruction can be stored within the microcodeROM 232 should a number of micro-ops be needed to accomplish theoperation. The trace cache 230 refers to a entry point programmablelogic array (PLA) to determine a correct micro-instruction pointer forreading the micro-code sequences to complete one or more instructions inaccordance with one embodiment from the micro-code ROM 232. After themicrocode ROM 232 finishes sequencing micro-ops for an instruction, thefront end 201 of the machine resumes fetching micro-ops from the tracecache 230.

The out-of-order execution engine 203 is where the instructions areprepared for execution. The out-of-order execution logic has a number ofbuffers to smooth out and re-order the flow of instructions to optimizeperformance as they go down the pipeline and get scheduled forexecution. The allocator logic allocates the machine buffers andresources that each uop needs in order to execute. The register renaminglogic renames logic registers onto entries in a register file. Theallocator also allocates an entry for each uop in one of the two uopqueues, one for memory operations and one for non-memory operations, infront of the instruction schedulers: memory scheduler, fast scheduler202, slow/general floating point scheduler 204, and simple floatingpoint scheduler 206. The uop schedulers 202, 204, 206, determine when auop is ready to execute based on the readiness of their dependent inputregister operand sources and the availability of the execution resourcesthe uops need to complete their operation. The fast scheduler 202 of oneembodiment can schedule on each half of the main clock cycle while theother schedulers can only schedule once per main processor clock cycle.The schedulers arbitrate for the dispatch ports to schedule uops forexecution.

Register files 208, 210, sit between the schedulers 202, 204, 206, andthe execution units 212, 214, 216, 218, 220, 222, 224 in the executionblock 211. There is a separate register file 208, 210, for integer andfloating point operations, respectively. Each register file 208, 210, ofone embodiment also includes a bypass network that can bypass or forwardjust completed results that have not yet been written into the registerfile to new dependent uops. The integer register file 208 and thefloating point register file 210 are also capable of communicating datawith the other. For one embodiment, the integer register file 208 issplit into two separate register files, one register file for the loworder 32 bits of data and a second register file for the high order 32bits of data. The floating point register file 210 of one embodiment has128 bit wide entries because floating point instructions typically haveoperands from 64 to 128 bits in width.

The execution block 211 contains the execution units 212, 214, 216, 218,220, 222, 224, where the instructions are actually executed. Thissection includes the register files 208, 210, that store the integer andfloating point data operand values that the micro-instructions need toexecute. The processor 200 of one embodiment is comprised of a number ofexecution units: address generation unit (AGU) 212, AGU 214, fast ALU216, fast ALU 218, slow ALU 220, floating point ALU 222, floating pointmove unit 224. For one embodiment, the floating point execution blocks222, 224, execute floating point, MMX, SIMD, and SSE, or otheroperations. The floating point ALU 222 of one embodiment includes a 64bit by 64 bit floating point divider to execute divide, square root, andremainder micro-ops. For embodiments of the present invention,instructions involving a floating point value may be handled with thefloating point hardware. In one embodiment, the ALU operations go to thehigh-speed ALU execution units 216, 218. The fast ALUs 216, 218, of oneembodiment can execute fast operations with an effective latency of halfa clock cycle. For one embodiment, most complex integer operations go tothe slow ALU 220 as the slow ALU 220 includes integer execution hardwarefor long latency type of operations, such as a multiplier, shifts, flaglogic, and branch processing. Memory load/store operations are executedby the AGUs 212, 214. For one embodiment, the integer ALUs 216, 218,220, are described in the context of performing integer operations on 64bit data operands. In alternative embodiments, the ALUs 216, 218, 220,can be implemented to support a variety of data bits including 16, 32,128, 256, etc. Similarly, the floating point units 222, 224, can beimplemented to support a range of operands having bits of variouswidths. For one embodiment, the floating point units 222, 224, canoperate on 128 bits wide packed data operands in conjunction with SIMDand multimedia instructions.

In one embodiment, the uops schedulers 202, 204, 206, dispatch dependentoperations before the parent load has finished executing. As uops arespeculatively scheduled and executed in processor 200, the processor 200also includes logic to handle memory misses. If a data load misses inthe data cache, there can be dependent operations in flight in thepipeline that have left the scheduler with temporarily incorrect data. Areplay mechanism tracks and re-executes instructions that use incorrectdata. Only the dependent operations need to be replayed and theindependent ones are allowed to complete. The schedulers and replaymechanism of one embodiment of a processor are also designed to catchinstruction sequences for text string comparison operations.

The term “registers” may refer to the on-board processor storagelocations that are used as part of instructions to identify operands. Inother words, registers may be those that are usable from the outside ofthe processor (from a programmer's perspective). However, the registersof an embodiment should not be limited in meaning to a particular typeof circuit. Rather, a register of an embodiment is capable of storingand providing data, and performing the functions described herein. Theregisters described herein can be implemented by circuitry within aprocessor using any number of different techniques, such as dedicatedphysical registers, dynamically allocated physical registers usingregister renaming, combinations of dedicated and dynamically allocatedphysical registers, etc. In one embodiment, integer registers storethirty-two bit integer data. A register file of one embodiment alsocontains eight multimedia SIMD registers for packed data. For thediscussions below, the registers are understood to be data registersdesigned to hold packed data, such as 64 bits wide MMX™ registers (alsoreferred to as ‘mm’ registers in some instances) in microprocessorsenabled with MMX technology from Intel Corporation of Santa Clara,Calif. These MMX registers, available in both integer and floating pointforms, can operate with packed data elements that accompany SIMD and SSEinstructions. Similarly, 128 bits wide XMM registers relating to SSE2,SSE3, SSE4, or beyond (referred to generically as “SSEx”) technology canalso be used to hold such packed data operands. In one embodiment, instoring packed data and integer data, the registers do not need todifferentiate between the two data types. In one embodiment, integer andfloating point are either contained in the same register file ordifferent register files. Furthermore, in one embodiment, floating pointand integer data may be stored in different registers or the sameregisters.

In the examples of the following figures, a number of data operands aredescribed. FIG. 3A illustrates various packed data type representationsin multimedia registers according to one embodiment of the presentinvention. FIG. 3A illustrates data types for a packed byte 310, apacked word 320, and a packed doubleword (dword) 330 for 128 bits wideoperands. The packed byte format 310 of this example is 128 bits longand contains sixteen packed byte data elements. A byte is defined hereas 8 bits of data. Information for each byte data element is stored inbit 7 through bit 0 for byte 0, bit 15 through bit 8 for byte 1, bit 23through bit 16 for byte 2, and finally bit 120 through bit 127 for byte15. Thus, all available bits are used in the register. This storagearrangement increases the storage efficiency of the processor. As well,with sixteen data elements accessed, one operation can now be performedon sixteen data elements in parallel.

Generally, a data element is an individual piece of data that is storedin a single register or memory location with other data elements of thesame length. In packed data sequences relating to SSEx technology, thenumber of data elements stored in a XMM register is 128 bits divided bythe length in bits of an individual data element. Similarly, in packeddata sequences relating to MMX and SSE technology, the number of dataelements stored in an MMX register is 64 bits divided by the length inbits of an individual data element. Although the data types illustratedin FIG. 3A are 128 bit long, embodiments of the present invention canalso operate with 64 bit wide or other sized operands. The packed wordformat 320 of this example is 128 bits long and contains eight packedword data elements. Each packed word contains sixteen bits ofinformation. The packed doubleword format 330 of FIG. 3A is 128 bitslong and contains four packed doubleword data elements. Each packeddoubleword data element contains thirty two bits of information. Apacked quadword is 128 bits long and contains two packed quad-word dataelements.

FIG. 3B illustrates alternative in-register data storage formats. Eachpacked data can include more than one independent data element. Threepacked data formats are illustrated; packed half 341, packed single 342,and packed double 343. One embodiment of packed half 341, packed single342, and packed double 343 contain fixed-point data elements. For analternative embodiment one or more of packed half 341, packed single342, and packed double 343 may contain floating-point data elements. Onealternative embodiment of packed half 341 is one hundred twenty-eightbits long containing eight 16-bit data elements. One embodiment ofpacked single 342 is one hundred twenty-eight bits long and containsfour 32-bit data elements. One embodiment of packed double 343 is onehundred twenty-eight bits long and contains two 64-bit data elements. Itwill be appreciated that such packed data formats may be furtherextended to other register lengths, for example, to 96-bits, 160-bits,192-bits, 224-bits, 256-bits or more.

FIG. 3C illustrates various signed and unsigned packed data typerepresentations in multimedia registers according to one embodiment ofthe present invention. Unsigned packed byte representation 344illustrates the storage of an unsigned packed byte in a SIMD register.Information for each byte data element is stored in bit seven throughbit zero for byte zero, bit fifteen through bit eight for byte one, bittwenty-three through bit sixteen for byte two, and finally bit onehundred twenty through bit one hundred twenty-seven for byte fifteen.Thus, all available bits are used in the register. This storagearrangement can increase the storage efficiency of the processor. Aswell, with sixteen data elements accessed, one operation can now beperformed on sixteen data elements in a parallel fashion. Signed packedbyte representation 345 illustrates the storage of a signed packed byte.Note that the eighth bit of every byte data element is the signindicator. Unsigned packed word representation 346 illustrates how wordseven through word zero are stored in a SIMD register. Signed packedword representation 347 is similar to the unsigned packed wordin-register representation 346. Note that the sixteenth bit of each worddata element is the sign indicator. Unsigned packed doublewordrepresentation 348 shows how doubleword data elements are stored. Signedpacked doubleword representation 349 is similar to unsigned packeddoubleword in-register representation 348. Note that the necessary signbit is the thirty-second bit of each doubleword data element.

FIG. 3D is a depiction of one embodiment of an operation encoding(opcode) format 360, having thirty-two or more bits, and register/memoryoperand addressing modes corresponding with a type of opcode formatdescribed in the “IA-32 Intel Architecture Software Developer's ManualVolume 2: Instruction Set Reference,” which is which is available fromIntel Corporation, Santa Clara, Calif. on the world-wide-web (www) atintel.com/design/litcentr. In one embodiment, and instruction may beencoded by one or more of fields 361 and 362. Up to two operandlocations per instruction may be identified, including up to two sourceoperand identifiers 364 and 365. For one embodiment, destination operandidentifier 366 is the same as source operand identifier 364, whereas inother embodiments they are different. For an alternative embodiment,destination operand identifier 366 is the same as source operandidentifier 365, whereas in other embodiments they are different. In oneembodiment, one of the source operands identified by source operandidentifiers 364 and 365 is overwritten by the results of the text stringcomparison operations, whereas in other embodiments identifier 364corresponds to a source register element and identifier 365 correspondsto a destination register element. For one embodiment, operandidentifiers 364 and 365 may be used to identify 32-bit or 64-bit sourceand destination operands.

FIG. 3E is a depiction of another alternative operation encoding(opcode) format 370, having forty or more bits. Opcode format 370corresponds with opcode format 360 and comprises an optional prefix byte378. An instruction according to one embodiment may be encoded by one ormore of fields 378, 371, and 372. Up to two operand locations perinstruction may be identified by source operand identifiers 374 and 375and by prefix byte 378. For one embodiment, prefix byte 378 may be usedto identify 32-bit or 64-bit source and destination operands. For oneembodiment, destination operand identifier 376 is the same as sourceoperand identifier 374, whereas in other embodiments they are different.For an alternative embodiment, destination operand identifier 376 is thesame as source operand identifier 375, whereas in other embodiments theyare different. In one embodiment, an instruction operates on one or moreof the operands identified by operand identifiers 374 and 375 and one ormore operands identified by the operand identifiers 374 and 375 isoverwritten by the results of the instruction, whereas in otherembodiments, operands identified by identifiers 374 and 375 are writtento another data element in another register. Opcode formats 360 and 370allow register to register, memory to register, register by memory,register by register, register by immediate, register to memoryaddressing specified in part by MOD fields 363 and 373 and by optionalscale-index-base and displacement bytes.

Turning next to FIG. 3F, in some alternative embodiments, 64 bit singleinstruction multiple data (SIMD) arithmetic operations may be performedthrough a coprocessor data processing (CDP) instruction. Operationencoding (opcode) format 380 depicts one such CDP instruction having CDPopcode fields 382 and 389. The type of CDP instruction, for alternativeembodiments, operations may be encoded by one or more of fields 383,384, 387, and 388. Up to three operand locations per instruction may beidentified, including up to two source operand identifiers 385 and 390and one destination operand identifier 386. One embodiment of thecoprocessor can operate on 8, 16, 32, and 64 bit values. For oneembodiment, an instruction is performed on integer data elements. Insome embodiments, an instruction may be executed conditionally, usingcondition field 381. For some embodiments, source data sizes may beencoded by field 383. In some embodiments, Zero (Z), negative (N), carry(C), and overflow (V) detection can be done on SIMD fields. For someinstructions, the type of saturation may be encoded by field 384.

FIG. 4A is a block diagram illustrating an in-order pipeline and aregister renaming stage, out-of-order issue/execution pipeline accordingto at least one embodiment of the invention. FIG. 4B is a block diagramillustrating an in-order architecture core and a register renaminglogic, out-of-order issue/execution logic to be included in a processoraccording to at least one embodiment of the invention. The solid linedboxes in FIG. 4A illustrate the in-order pipeline, while the dashedlined boxes illustrates the register renaming, out-of-orderissue/execution pipeline. Similarly, the solid lined boxes in FIG. 4Billustrate the in-order architecture logic, while the dashed lined boxesillustrates the register renaming logic and out-of-order issue/executionlogic.

In FIG. 4A, a processor pipeline 400 includes a fetch stage 402, alength decode stage 404, a decode stage 406, an allocation stage 408, arenaming stage 410, a scheduling (also known as a dispatch or issue)stage 412, a register read/memory read stage 414, an execute stage 416,a write back/memory write stage 418, an exception handling stage 422,and a commit stage 424.

In FIG. 4B, arrows denote a coupling between two or more units and thedirection of the arrow indicates a direction of data flow between thoseunits. FIG. 4B shows processor core 490 including a front end unit 430coupled to an execution engine unit 450, and both are coupled to amemory unit 470.

The core 490 may be a reduced instruction set computing (RISC) core, acomplex instruction set computing (CISC) core, a very long instructionword (VLIW) core, or a hybrid or alternative core type. As yet anotheroption, the core 490 may be a special-purpose core, such as, forexample, a network or communication core, compression engine, graphicscore, or the like.

The front end unit 430 includes a branch prediction unit 432 coupled toan instruction cache unit 434, which is coupled to an instructiontranslation lookaside buffer (TLB) 436, which is coupled to aninstruction fetch unit 438, which is coupled to a decode unit 440. Thedecode unit or decoder may decode instructions, and generate as anoutput one or more micro-operations, micro-code entry points,microinstructions, other instructions, or other control signals, whichare decoded from, or which otherwise reflect, or are derived from, theoriginal instructions. The decoder may be implemented using variousdifferent mechanisms. Examples of suitable mechanisms include, but arenot limited to, look-up tables, hardware implementations, programmablelogic arrays (PLAs), microcode read only memories (ROMs), etc. Theinstruction cache unit 434 is further coupled to a level 2 (L2) cacheunit 476 in the memory unit 470. The decode unit 440 is coupled to arename/allocator unit 452 in the execution engine unit 450.

The execution engine unit 450 includes the rename/allocator unit 452coupled to a retirement unit 454 and a set of one or more schedulerunit(s) 456. The scheduler unit(s) 456 represents any number ofdifferent schedulers, including reservations stations, centralinstruction window, etc. The scheduler unit(s) 456 is coupled to thephysical register file(s) unit(s) 458. Each of the physical registerfile(s) units 458 represents one or more physical register files,different ones of which store one or more different data types, such asscalar integer, scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point, etc., status (e.g., aninstruction pointer that is the address of the next instruction to beexecuted), etc. The physical register file(s) unit(s) 458 is overlappedby the retirement unit 154 to illustrate various ways in which registerrenaming and out-of-order execution may be implemented (e.g., using areorder buffer(s) and a retirement register file(s), using a futurefile(s), a history buffer(s), and a retirement register file(s); using aregister maps and a pool of registers; etc.). Generally, thearchitectural registers are visible from the outside of the processor orfrom a programmer's perspective. The registers are not limited to anyknown particular type of circuit. Various different types of registersare suitable as long as they are capable of storing and providing dataas described herein. Examples of suitable registers include, but are notlimited to, dedicated physical registers, dynamically allocated physicalregisters using register renaming, combinations of dedicated anddynamically allocated physical registers, etc. The retirement unit 454and the physical register file(s) unit(s) 458 are coupled to theexecution cluster(s) 460. The execution cluster(s) 460 includes a set ofone or more execution units 162 and a set of one or more memory accessunits 464. The execution units 462 may perform various operations (e.g.,shifts, addition, subtraction, multiplication) and on various types ofdata (e.g., scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point). While some embodimentsmay include a number of execution units dedicated to specific functionsor sets of functions, other embodiments may include only one executionunit or multiple execution units that all perform all functions. Thescheduler unit(s) 456, physical register file(s) unit(s) 458, andexecution cluster(s) 460 are shown as being possibly plural becausecertain embodiments create separate pipelines for certain types ofdata/operations (e.g., a scalar integer pipeline, a scalar floatingpoint/packed integer/packed floating point/vector integer/vectorfloating point pipeline, and/or a memory access pipeline that each havetheir own scheduler unit, physical register file(s) unit, and/orexecution cluster—and in the case of a separate memory access pipeline,certain embodiments are implemented in which only the execution clusterof this pipeline has the memory access unit(s) 464). It should also beunderstood that where separate pipelines are used, one or more of thesepipelines may be out-of-order issue/execution and the rest in-order.

The set of memory access units 464 is coupled to the memory unit 470,which includes a data TLB unit 472 coupled to a data cache unit 474coupled to a level 2 (L2) cache unit 476. In one exemplary embodiment,the memory access units 464 may include a load unit, a store addressunit, and a store data unit, each of which is coupled to the data TLBunit 472 in the memory unit 470. The L2 cache unit 476 is coupled to oneor more other levels of cache and eventually to a main memory.

By way of example, the exemplary register renaming, out-of-orderissue/execution core architecture may implement the pipeline 400 asfollows: 1) the instruction fetch 438 performs the fetch and lengthdecoding stages 402 and 404; 2) the decode unit 440 performs the decodestage 406; 3) the rename/allocator unit 452 performs the allocationstage 408 and renaming stage 410; 4) the scheduler unit(s) 456 performsthe schedule stage 412; 5) the physical register file(s) unit(s) 458 andthe memory unit 470 perform the register read/memory read stage 414; theexecution cluster 460 perform the execute stage 416; 6) the memory unit470 and the physical register file(s) unit(s) 458 perform the writeback/memory write stage 418; 7) various units may be involved in theexception handling stage 422; and 8) the retirement unit 454 and thephysical register file(s) unit(s) 458 perform the commit stage 424.

The core 490 may support one or more instructions sets (e.g., the x86instruction set (with some extensions that have been added with newerversions); the MIPS instruction set of MIPS Technologies of Sunnyvale,Calif.; the ARM instruction set (with optional additional extensionssuch as NEON) of ARM Holdings of Sunnyvale, Calif.).

It should be understood that the core may support multithreading(executing two or more parallel sets of operations or threads), and maydo so in a variety of ways including time sliced multithreading,simultaneous multithreading (where a single physical core provides alogical core for each of the threads that physical core issimultaneously multithreading), or a combination thereof (e.g., timesliced fetching and decoding and simultaneous multithreading thereaftersuch as in the Intel® Hyperthreading technology).

While register renaming is described in the context of out-of-orderexecution, it should be understood that register renaming may be used inan in-order architecture. While the illustrated embodiment of theprocessor also includes a separate instruction and data cache units434/474 and a shared L2 cache unit 476, alternative embodiments may havea single internal cache for both instructions and data, such as, forexample, a Level 1 (L1) internal cache, or multiple levels of internalcache. In some embodiments, the system may include a combination of aninternal cache and an external cache that is external to the core and/orthe processor. Alternatively, all of the cache may be external to thecore and/or the processor.

FIG. 5 is a block diagram of a single core processor and a multicoreprocessor 500 with integrated memory controller and graphics accordingto embodiments of the invention. The solid lined boxes in FIG. 5illustrate a processor 500 with a single core 502A, a system agent 510,a set of one or more bus controller units 516, while the optionaladdition of the dashed lined boxes illustrates an alternative processor500 with multiple cores 502A-N, a set of one or more integrated memorycontroller unit(s) 514 in the system agent unit 510, and an integratedgraphics logic 508.

The memory hierarchy includes one or more levels of cache within thecores, a set or one or more shared cache units 506, and external memory(not shown) coupled to the set of integrated memory controller units514. The set of shared cache units 506 may include one or more mid-levelcaches, such as level 2 (L2), level 3 (L3), level 4 (L4), or otherlevels of cache, a last level cache (LLC), and/or combinations thereof.While in one embodiment a ring based interconnect unit 512 interconnectsthe integrated graphics logic 508, the set of shared cache units 506,and the system agent unit 510, alternative embodiments may use anynumber of well-known techniques for interconnecting such units.

In some embodiments, one or more of the cores 502A-N are capable ofmulti-threading. The system agent 510 includes those componentscoordinating and operating cores 502A-N. The system agent unit 510 mayinclude for example a power control unit (PCU) and a display unit. ThePCU may be or include logic and components needed for regulating thepower state of the cores 502A-N and the integrated graphics logic 508.The display unit is for driving one or more externally connecteddisplays.

The cores 502A-N may be homogenous or heterogeneous in terms ofarchitecture and/or instruction set. For example, some of the cores502A-N may be in order while others are out-of-order. As anotherexample, two or more of the cores 502A-N may be capable of execution thesame instruction set, while others may be capable of executing only asubset of that instruction set or a different instruction set.

The processor may be a general-purpose processor, such as a Core™ i3,i5, i7, 2 Duo and Quad, Xeon™, Itanium™, XScale™ or StrongARM™processor, which are available from Intel Corporation, of Santa Clara,Calif. Alternatively, the processor may be from another company, such asARM Holdings, Ltd, MIPS, etc. The processor may be a special-purposeprocessor, such as, for example, a network or communication processor,compression engine, graphics processor, co-processor, embeddedprocessor, or the like. The processor may be implemented on one or morechips. The processor 500 may be a part of and/or may be implemented onone or more substrates using any of a number of process technologies,such as, for example, BiCMOS, CMOS, or NMOS.

FIGS. 6-8 are exemplary systems suitable for including the processor500, while FIG. 9 is an exemplary system on a chip (SoC) that mayinclude one or more of the cores 502. Other system designs andconfigurations known in the arts for laptops, desktops, handheld PCs,personal digital assistants, engineering workstations, servers, networkdevices, network hubs, switches, embedded processors, digital signalprocessors (DSPs), graphics devices, video game devices, set-top boxes,micro controllers, cell phones, portable media players, hand helddevices, and various other electronic devices, are also suitable. Ingeneral, a huge variety of systems or electronic devices capable ofincorporating a processor and/or other execution logic as disclosedherein are generally suitable.

Referring now to FIG. 6, shown is a block diagram of a system 600 inaccordance with one embodiment of the present invention. The system 600may include one or more processors 610, 615, which are coupled tographics memory controller hub (GMCH) 620. The optional nature ofadditional processors 615 is denoted in FIG. 6 with broken lines.

Each processor 610,615 may be some version of the processor 500.However, it should be noted that it is unlikely that integrated graphicslogic and integrated memory control units would exist in the processors610,615. FIG. 6 illustrates that the GMCH 620 may be coupled to a memory640 that may be, for example, a dynamic random access memory (DRAM). TheDRAM may, for at least one embodiment, be associated with a non-volatilecache.

The GMCH 620 may be a chipset, or a portion of a chipset. The GMCH 620may communicate with the processor(s) 610, 615 and control interactionbetween the processor(s) 610, 615 and memory 640. The GMCH 620 may alsoact as an accelerated bus interface between the processor(s) 610, 615and other elements of the system 600. For at least one embodiment, theGMCH 620 communicates with the processor(s) 610, 615 via a multi-dropbus, such as a frontside bus (FSB) 695.

Furthermore, GMCH 620 is coupled to a display 645 (such as a flat paneldisplay). GMCH 620 may include an integrated graphics accelerator. GMCH620 is further coupled to an input/output (I/O) controller hub (ICH)650, which may be used to couple various peripheral devices to system600. Shown for example in the embodiment of FIG. 6 is an externalgraphics device 660, which may be a discrete graphics device coupled toICH 650, along with another peripheral device 670.

Alternatively, additional or different processors may also be present inthe system 600. For example, additional processor(s) 615 may includeadditional processors(s) that are the same as processor 610, additionalprocessor(s) that are heterogeneous or asymmetric to processor 610,accelerators (such as, e.g., graphics accelerators or digital signalprocessing (DSP) units), field programmable gate arrays, or any otherprocessor. There can be a variety of differences between the physicalresources 610, 615 in terms of a spectrum of metrics of merit includingarchitectural, micro-architectural, thermal, power consumptioncharacteristics, and the like. These differences may effectivelymanifest themselves as asymmetry and heterogeneity amongst theprocessors 610, 615. For at least one embodiment, the various processors610, 615 may reside in the same die package.

Referring now to FIG. 7, shown is a block diagram of a second system 700in accordance with an embodiment of the present invention. As shown inFIG. 7, multiprocessor system 700 is a point-to-point interconnectsystem, and includes a first processor 770 and a second processor 780coupled via a point-to-point interconnect 750. Each of processors 770and 780 may be some version of the processor 500 as one or more of theprocessors 610,615.

While shown with only two processors 770, 780, it is to be understoodthat the scope of the present invention is not so limited. In otherembodiments, one or more additional processors may be present in a givenprocessor.

Processors 770 and 780 are shown including integrated memory controllerunits 772 and 782, respectively. Processor 770 also includes as part ofits bus controller units point-to-point (P-P) interfaces 776 and 778;similarly, second processor 780 includes P-P interfaces 786 and 788.Processors 770, 780 may exchange information via a point-to-point (P-P)interface 750 using P-P interface circuits 778, 788. As shown in FIG. 7,IMCs 772 and 782 couple the processors to respective memories, namely amemory 732 and a memory 734, which may be portions of main memorylocally attached to the respective processors.

Processors 770, 780 may each exchange information with a chipset 790 viaindividual P-P interfaces 752, 754 using point to point interfacecircuits 776, 794, 786, 798. Chipset 790 may also exchange informationwith a high-performance graphics circuit 738 via a high-performancegraphics interface 739.

A shared cache (not shown) may be included in either processor oroutside of both processors, yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode.

Chipset 790 may be coupled to a first bus 716 via an interface 796. Inone embodiment, first bus 716 may be a Peripheral Component Interconnect(PCI) bus, or a bus such as a PCI Express bus or another thirdgeneration I/O interconnect bus, although the scope of the presentinvention is not so limited.

As shown in FIG. 7, various I/O devices 714 may be coupled to first bus716, along with a bus bridge 718 which couples first bus 716 to a secondbus 720. In one embodiment, second bus 720 may be a low pin count (LPC)bus. Various devices may be coupled to second bus 720 including, forexample, a keyboard and/or mouse 722, communication devices 727 and astorage unit 728 such as a disk drive or other mass storage device whichmay include instructions/code and data 730, in one embodiment. Further,an audio I/O 724 may be coupled to second bus 720. Note that otherarchitectures are possible. For example, instead of the point-to-pointarchitecture of FIG. 7, a system may implement a multi-drop bus or othersuch architecture.

Referring now to FIG. 8, shown is a block diagram of a third system 800in accordance with an embodiment of the present invention. Like elementsin FIGS. 7 and 8 bear like reference numerals, and certain aspects ofFIG. 7 have been omitted from FIG. 8 in order to avoid obscuring otheraspects of FIG. 8.

FIG. 8 illustrates that the processors 870, 880 may include integratedmemory and I/O control logic (“CL”) 872 and 882, respectively. For atleast one embodiment, the CL 872, 882 may include integrated memorycontroller units such as that described above in connection with FIGS. 5and 7. In addition. CL 872, 882 may also include I/O control logic. FIG.8 illustrates that not only are the memories 832, 834 coupled to the CL872, 882, but also that I/O devices 814 are also coupled to the controllogic 872, 882. Legacy I/O devices 815 are coupled to the chipset 890.

Referring now to FIG. 9, shown is a block diagram of a SoC 900 inaccordance with an embodiment of the present invention. Similar elementsin FIG. 5 bear like reference numerals. Also, dashed lined boxes areoptional features on more advanced SoCs. In FIG. 9, an interconnectunit(s) 902 is coupled to: an application processor 910 which includes aset of one or more cores 902A-N and shared cache unit(s) 906; a systemagent unit 910; a bus controller unit(s) 916; an integrated memorycontroller unit(s) 914; a set or one or more media processors 920 whichmay include integrated graphics logic 908, an image processor 924 forproviding still and/or video camera functionality, an audio processor926 for providing hardware audio acceleration, and a video processor 928for providing video encode/decode acceleration; an static random accessmemory (SRAM) unit 930; a direct memory access (DMA) unit 932; and adisplay unit 940 for coupling to one or more external displays.

FIG. 10 illustrates a processor containing a central processing unit(CPU) and a graphics processing unit (GPU), which may perform at leastone instruction according to one embodiment. In one embodiment, aninstruction to perform operations according to at least one embodimentcould be performed by the CPU. In another embodiment, the instructioncould be performed by the GPU. In still another embodiment, theinstruction may be performed through a combination of operationsperformed by the GPU and the CPU. For example, in one embodiment, aninstruction in accordance with one embodiment may be received anddecoded for execution on the GPU. However, one or more operations withinthe decoded instruction may be performed by a CPU and the resultreturned to the GPU for final retirement of the instruction. Conversely,in some embodiments, the CPU may act as the primary processor and theGPU as the co-processor.

In some embodiments, instructions that benefit from highly parallel,throughput processors may be performed by the GPU, while instructionsthat benefit from the performance of processors that benefit from deeplypipelined architectures may be performed by the CPU. For example,graphics, scientific applications, financial applications and otherparallel workloads may benefit from the performance of the GPU and beexecuted accordingly, whereas more sequential applications, such asoperating system kernel or application code may be better suited for theCPU.

In FIG. 10, processor 1000 includes a CPU 1005, GPU 1010, imageprocessor 1015, video processor 1020, USB controller 1025, UARTcontroller 1030, SPI/SDIO controller 1035, display device 1040, memoryinterface controller 1045, MIPI controller 1050, flash memory controller1055, dual data rate (DDR) controller 1060, security engine 1065, andI2S/I2C controller 1070. Other logic and circuits may be included in theprocessor of FIG. 10, including more CPUs or GPUs and other peripheralinterface controllers.

One or more aspects of at least one embodiment may be implemented byrepresentative data stored on a machine-readable medium which representsvarious logic within the processor, which when read by a machine causesthe machine to fabricate logic to perform the techniques describedherein. Such representations, known as “IP cores” may be stored on atangible, machine readable medium (“tape”) and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor. For example, IPcores, such as the Cortex™ family of processors developed by ARMHoldings, Ltd. and Loongson IP cores developed the Institute ofComputing Technology (ICT) of the Chinese Academy of Sciences may belicensed or sold to various customers or licensees, such as TexasInstruments, Qualcomm, Apple, or Samsung and implemented in processorsproduced by these customers or licensees.

FIG. 11 shows a block diagram illustrating the development of IP coresaccording to one embodiment. Storage 1130 includes simulation software1120 and/or hardware or software model 1110. In one embodiment, the datarepresenting the IP core design can be provided to the storage 1130 viamemory 1140 (e.g., hard disk), wired connection (e.g., internet) 1150 orwireless connection 1160. The IP core information generated by thesimulation tool and model can then be transmitted to a fabricationfacility where it can be fabricated by a 3rd party to perform at leastone instruction in accordance with at least one embodiment.

In some embodiments, one or more instructions may correspond to a firsttype or architecture (e.g., x86) and be translated or emulated on aprocessor of a different type or architecture (e.g., ARM). Aninstruction, according to one embodiment, may therefore be performed onany processor or processor type, including ARM, x86, MIPS, a GPU, orother processor type or architecture.

FIG. 12 illustrates how an instruction of a first type is emulated by aprocessor of a different type, according to one embodiment. In FIG. 12,program 1205 contains some instructions that may perform the same orsubstantially the same function as an instruction according to oneembodiment. However the instructions of program 1205 may be of a typeand/or format that is different or incompatible with processor 1215,meaning the instructions of the type in program 1205 may not be able toexecuted natively by the processor 1215. However, with the help ofemulation logic, 1210, the instructions of program 1205 are translatedinto instructions that are natively capable of being executed by theprocessor 1215. In one embodiment, the emulation logic is embodied inhardware. In another embodiment, the emulation logic is embodied in atangible, machine-readable medium containing software to translateinstructions of the type in the program 1205 into the type nativelyexecutable by the processor 1215. In other embodiments, emulation logicis a combination of fixed-function or programmable hardware and aprogram stored on a tangible, machine-readable medium. In oneembodiment, the processor contains the emulation logic, whereas in otherembodiments, the emulation logic exists outside of the processor and isprovided by a third party. In one embodiment, the processor is capableof loading the emulation logic embodied in a tangible, machine-readablemedium containing software by executing microcode or firmware containedin or associated with the processor.

FIG. 13 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention. In the illustrated embodiment, the instructionconverter is a software instruction converter, although alternativelythe instruction converter may be implemented in software, firmware,hardware, or various combinations thereof. FIG. 13 shows a program in ahigh level language 1302 may be compiled using an x86 compiler 1304 togenerate x86 binary code 1306 that may be natively executed by aprocessor with at least one x86 instruction set core 1316. The processorwith at least one x86 instruction set core 1316 represents any processorthat can perform substantially the same functions as a Intel processorwith at least one x86 instruction set core by compatibly executing orotherwise processing (1) a substantial portion of the instruction set ofthe Intel x86 instruction set core or (2) object code versions ofapplications or other software targeted to run on an Intel processorwith at least one x86 instruction set core, in order to achievesubstantially the same result as an Intel processor with at least onex86 instruction set core. The x86 compiler 1304 represents a compilerthat is operable to generate x86 binary code 1306 (e.g., object code)that can, with or without additional linkage processing, be executed onthe processor with at least one x86 instruction set core 1316.Similarly, FIG. 13 shows the program in the high level language 1302 maybe compiled using an alternative instruction set compiler 1308 togenerate alternative instruction set binary code 1310 that may benatively executed by a processor without at least one x86 instructionset core 1314 (e.g., a processor with cores that execute the MIPSinstruction set of MIPS Technologies of Sunnyvale, Calif. and/or thatexecute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.).The instruction converter 1312 is used to convert the x86 binary code1306 into code that may be natively executed by the processor without anx86 instruction set core 1314. This converted code is not likely to bethe same as the alternative instruction set binary code 1310 because aninstruction converter capable of this is difficult to make; however, theconverted code will accomplish the general operation and be made up ofinstructions from the alternative instruction set. Thus, the instructionconverter 1312 represents software, firmware, hardware, or a combinationthereof that, through emulation, simulation or any other process, allowsa processor or other electronic device that does not have an x86instruction set processor or core to execute the x86 binary code 1306.

Multiphase Power Control Flow

Instruction and logic for performing a multiphase power control flow aredescribed. In one embodiment, the power control flow is a flow forputting part of a device, such as, for example, an integrated circuit(e.g., a processor, system-on-chip (SoC), etc.), into a sleep state. Thepart of the device may be, for example, a core, controller, orintellectual property (IP) block, or some other part of the device. Inone embodiment, the sleep state is a deep sleep state, such as, forexample, a C6 C-state. In another embodiment, the power control flow isa flow for performing dynamic voltage and frequency scaling (DVFS) withrespect to a part of the device.

In one embodiment, the techniques described herein are implemented in anintegrated circuit that comprises multiple processing entities (e.g.,cores, memory controller, etc.) to execute operations, a powercontroller coupled to the processing entities to control powermanagement for those entities, and multiple agents that each perform apower control flow (e.g., a power down flow) for one of the processingentities.

In one embodiment, the agents separately schedule, using a scheduler,and execute multiple power control flow phases in response to parallelrequests from the power controller. The phases can be scheduled by theagent's scheduler for performance with the processing entity associatedwith the agent based on the scheduler of the agent and that processingentity. In one embodiment, the techniques described herein removedependencies between different phases of a power down flow, which inturn removes the serial nature of the phases. Without the dependencies,a scheduler can schedule the phases to occur separately from the otherphases. In one embodiment, the scheduler can also skip certainoperations for a processing entity where such operations are notnecessary for the power down flow.

In one embodiment, each agent comprises circuitry to perform a powerdown flow for its associated processing entity according to a pluralityof finite state machines (FSMs). In one embodiment, the FSMs set forthoperations to transition one of the processing entities into and out ofa deep sleep state (e.g., C6 power state) and/or to enable one of theprocessing entities to undergo voltage and frequency scaling.

In one embodiment, each FSM specifies operations for one phase of thepower down flow. Each agent accesses the FSMs and schedules theoperations specified by each FSM in response to receiving the requestsfrom the power controller. In one embodiment, a request to perform theoperations of each FSM are sent from the power controller in parallelwith requests to perform the other FSMs. After completing the powercontrol flow, in one embodiment, each agent sends acknowledgements backto the power controller in parallel, where each acknowledgement is toacknowledge completion of one of the phases. In one embodiment, theseacknowledgements are only sent by the agent upon completion of all thepower control flow phases. Thus, the scheduler manages all pendingrequest for power down flow and manage all the acknowledgements. Theability to communicate requests for phases in parallel (e.g., in onemessage) from the power controller and sending acknowledgements inparallel (e.g., in one message) by the agents hides the communicationlatency that is associated with performing the power control flow andreduces FSM stall between different phases. By removing most ofcommunications associated with performing each of the phases defined bythe FSMs, latency to complete all the phases can be reduced to half andeven more.

In one embodiment, at least one of the plurality of agents sends atleast one of the acknowledgements (with the other acknowledgements)indicating completion of one or more of the plurality of phases thatwere not performed for its associated processing entity because thosephases were not relevant to the processing entity.

In prior implementations in which a single FSM included all the phases,the PCU would communication with the processing entity a request toperform one phase at a time and would wait to receive theacknowledgement that the phase was completed before sending the requestfor the next phase to be performed. This meant that the processingentity had to wait to get the next request while the PCU processed theacknowledgement for the previous phase. Furthermore, once the single FSMwas started, all the phases had to be completed, and there was no wayinto which phases could be overlapped with each other and phases, orparts thereof, could be skipped. Moreover, in one embodiment, a requestto perform a phase can be sent multiple times. This means that differentphases could be overlapped in their execution.

In one embodiment, the techniques described herein reduce latencies ofDVFS and C6 enter/exit power flow. The communication itself for someimplementations would consume ˜4 usec. By reducing the communication toone message with parallel requests to perform the phases of the powerdown flow and one message with parallel acknowledgements that therequests have been completed, this communication latency is reduced from˜4 usec to 2 usec. This translates into a 15% performance improvement.In server cases, the communication latencies is much higher and gainmuch bigger. The reduced latency associated with the use of thesetechniques allows the power flow to be executed more frequently due toreduced cost, which in the end brings lower power and better performancefor devices incorporating these techniques.

Note that in another embodiment the requests to perform the power flowcontrol phase are sent to a power management agent serially. In such acase, the power management agent may wait to receive all of the requestsbefore scheduling operations. In another embodiment, the powermanagement agent schedules operations as the phase requests arereceived. In yet another embodiment, the power management agent sendsthe acknowledgements serially.

FIG. 14 is a block diagram of a processor in accordance with anembodiment. Referring to FIG. 14, processor 1400 may be a multicoreprocessor including a plurality of cores 1410 a-1410 n. In oneembodiment, each such core may be of a single domain or an independentpower domain and can be configured to enter and exit active statesand/or an not active states. This may be based on the workload of eachof cores 1410 a-1410 n.

In addition to cores 1410 a-1410 n, additional processing engines areoptionally present within the processor, such as those described above,including, but not limited to, at least one graphics unit (not shown forease of illustration) which may include one or more graphics processingunits (GPUs) to perform graphics processing as well as to possiblyexecute general purpose operations on the graphics processor. Inaddition, at least one image signal processor (not shown for ease ofillustration) may be present to process incoming image data receivedfrom one or more capture devices, either internal to the process oroff-chip. All of these various processing units, including cores 1410a-1410 n, and any graphics unit and image signal processor couple tointerconnect 1415.

The various cores may be coupled via an interconnect 1415 to an uncore1420 that includes various components. Interconnect 1415 may comprise,but is not limited to, a fabric, a ring architecture, point-to-pointinterconnect, etc. Interconnect 1415 may act as a cache coherent on-dieinterconnect that in turn couples to an integrated memory controller1440 in uncore 1420. In turn, memory controller 1440 controlscommunications with a system memory 1460, such as, for example, adynamic random access memory (DRAM).

In one embodiment, uncore 1420 includes components that performfunctions of the processor that are not in the core. These may include,but are not limited to, memory access functions, input/output (I/O)functions, and/or clocking functions. In one embodiment, these functionsare closely connected with the core. In one embodiment, uncore 1420comprises a system agent to perform one or more of these operations.

In one embodiment, uncore 1420 includes various interfaces 1450 and apower control unit (PCU) 1455, which controls power consumption ofcomponents in the processor including, but not limited to, cores 1410a-1410 n, memory controller 1440. In one embodiment, PCU 1455 makesdecisions on which power management states (e.g., microprocessorperformance (P) states, microprocessor throttle (T) states,microprocessor and package idle (C) states, system sleep (S) states,etc.) to enter. In one embodiment, PCU 1455 includes dynamic voltage andfrequency scaling (DVFS) control logic 1459 in accordance with anembodiment. In one embodiment, DVFS control logic 1459 is configured toenable independent V/F control of multiple domains of the core 1410a-1410 n and/or portions of uncore 1420 (e.g., memory controller 1440).This may be based on activity information, configuration information,environmental information, and heuristics. In one embodiment, this isbased on inputs on temperature, current, power and operating system (OS)states.

In one embodiment, processor 1400 communicates with a system memory1460, e.g., via a memory bus. In addition, using interfaces 1450, aconnection can be made to various off-chip components such as, forexample, peripheral devices, mass storage and so forth. While shown withthis particular implementation in the embodiment of FIG. 14, the scopeof the present invention is not limited in this regard.

As further shown, each core 1410 includes a clock interface 1405, whichmay be implemented as a bubble generator first-in first-out (BGF) clockcrossing buffer to enable interconnection to a interconnect 1415. Eachcore also includes core memory. In one embodiment, core memory 1406 islocated outside of each core. An example of such a memory is shown asshared cache memory 1430 (e.g., static random access memory (SRAM), LastLevel Cache (LLC), etc.). In another embodiment, the core memory is partof the core itself, such as core memories 1406A-N (e.g., static randomaccess memory (SRAM), Last Level Cache (LLC), etc.). In one embodiment,core memory 1406 is powered using the same power rail that suppliespower to a rest of its core. However, in one embodiment, when enteringand during one or more reduced power consumption states (e.g., C6), aswitch couples core memory 1406 to another power rail. Such a power railmay be a lower voltage power rail.

FIG. 15 illustrates one embodiment of supplying power to a core.Referring to FIG. 15, power rail 1501 provides power to core throughpower gate 1502. Power gate 1502 is controlled to enable or disablepower to the core via one or more control signals 1503. In oneembodiment, control signal 1503 is from an agent of the core. Gate logic1504 enables either power from power rail 1501 or a different powerrail, namely power rail 1505 to provide power to the core memory (e.g.,SRAM) in the core. In one embodiment, gate logic 1504 is controlled byone or more control signals 1506 from an agent of the core to providethe core memory with power from power rail 1501 when the core is in anactive state and provide the core memory with power from power rail 1505during one or more reduced power consumption states (e.g., C-state C6).In one embodiment, gate logic 1504 comprises one or more power gates. Inanother embodiment, gate logic 1504 comprises one or more switches.

Each core 1410 a-1410 n and other processing unit (e.g., memorycontroller) is coupled to receive a clock signal from a clock generator(e.g., phase locked loop (PLL)). In one embodiment, the clock generatormay be part of the core. In another embodiment, the clock generator ispart of uncore 1420. While operating in one or more reduced powerconsumption states (e.g., C-state C6), the clock signal from the clockgenerator is gated and/or the clock generator is disabled. In oneembodiment, this is controlled by an agent of the core. FIG. 16illustrates one embodiment of the clock gating of the clock signal ofthe core. Referring to FIG. 16, a PLL 1601 receives a reference clock1600 and generates a core clock signal 1603, which is used to clock core1605. In one embodiment, PLL 1601 is controlled by control signals 1610.In one embodiment, control signals 1510 disable and enable PLL 1601 andindicate a clock ratio that is to be used by PLL 1601 in generating coreclock signal 1603. In one embodiment, control signals 1610 are generatedby an agent of core 1605. Clock gating logic 1604 is operable to gatecore clock signal 1603 to core 1605. In one embodiment, control signals1611 from an agent of core 1605 gate core clock signal 1603 during oneor more reduced power consumption states (e.g., C-state C6).

Referring back to FIG. 14, each of the cores and components alsoincludes a power management agent, such as, for example, powermanagement agents 1411 a-1411 n for cores 1410 a-1410 n and memorycontroller power management agent 1441 for memory controller 1440. Notethat other components in the processor may have a corresponding powermanagement agent as well. In one embodiment, power management agents1411 a-1411 n are part of uncore 1420, instead of being within eachcore, such as shown as power management agents 1480.

In one embodiment, the power management agents perform the power downflow for each of their respective component. For example, the agents forthe cores perform the core power down flow. In one embodiment, this isaccomplished by providing each of agents with circuitry to performoperations associated with a plurality of finite state machines (FSMs),one for each phase of the power down flow, and a scheduler that controlsthe performance of each of the phases in response to requests to havethe phases performed received from the PCU. The operations of the FSMsare stored in an agent memory that might be part of and/or accessible bythe agent. In one embodiment, the operations of the FSMs are implementedin firmware that is used by the agent to perform the operations.

In one embodiment, the power down flow is divided into five phases, witha FSM for each phase. By performing all five phases, the power down flowis completed. In one embodiment, the PCU sends the requests for themultiple phases to an agent in parallel that indicate that the PCU wantsto agent to perform the power down flow for its associated core (orcomponent). In the case where the power down flow is divided into fivephases, the PCU sends five requests in parallel to the agent. FIG. 23illustrates the sending of five requests, one for each of the phases1-5, in one embodiment of the power down flow in parallel as part of onemessage. In response thereto, the scheduler of the agent for that coreschedules the operations needed to complete each phase to complete thepower down flow. After all the phases have been completed, the agentsends acknowledgements, one for each completed phase, in parallel to thePCU. In another embodiment, the PCU sends a single request to the agentto perform all the phases (e.g., five phases set forth by the five FSMs)and receives a single acknowledgement back from the agent when all thephases have been completed.

In one embodiment, the agents are part of the component (e.g., core)itself. In another embodiment, the agents are part of uncore 1420 oranother area outside of their respective component.

Note that by dividing the power down flow into multiple separate phases,and their corresponding FSMs, any dependencies between the FSMs can beremoved and the operations for each FSM can be scheduled independentlyof the other FSMs.

FIG. 17 illustrates one embodiment of the five FSM phases. Note thatwhile FIG. 17 is limited to cores, the FSMs may be used for othercomponents that are part of the processor or another integrated circuit.Referring to FIG. 17, the plurality of finite state machines 1700comprises: a first FSM to place the core in a quiesced state (1701); asecond FSM to block one or more interfaces to the core (1702); a thirdFSM to stop clocking of the core (1703); a fourth FSM to exit thereduced power consumption state (1704); and a fifth FSM to cause thecore to resume executing instructions (1705).

FIG. 18 is a flow diagram of one embodiment of a FSM process to placethe core in a quiesced state. In one embodiment, the process isperformed by processing logic that may comprise hardware (circuitry,dedicated logic, etc.), software (such as is run on a general purposecomputer system or a dedicated machine), firmware, or a combination ofthe three.

Referring to FIG. 18, the process begins by processing logic stoppingcore operation (processing block 1801). After stopping the coreoperation, the core is no longer generating transactions to memory. Thenprocessing logic completes any thermal throttling of which the core is apart (processing block 1802). Afterward, processing logic sends the corepower down state (processing block 1803). In one embodiment, once theseoperations have been completed, the agent for the core sends anacknowledgement that this phase has been completed. In one embodiment,this acknowledgement is sent in parallel with the acknowledgements thatthe other phases have been completed.

FIG. 19 is a flow diagram of one embodiment of a FSM process to blockone or more interfaces to the core. In one embodiment, the process isperformed by processing logic that may comprise hardware (circuitry,dedicated logic, etc.), software (such as is run on a general purposecomputer system or a dedicated machine), firmware, or a combination ofthe three.

Referring to FIG. 19, the process begins by processing logic activatingmechanism to respond to snoop operations with an indication of that thecore does not have any data relevant to the snoop (processing block1901). This is necessary when the path from the I/O subsystem is stillopen for snoops. Next, processing logic stops the interconnect interfaceto the core (processing block 1902). In one embodiment, stopping theinterconnect interface comprises stopping the IDI (in-die interconnect)interface. After the I/O interferes to the core has been shut down, thecore cannot receive upstream traffic.

Once the interconnect interface has been stopped, processing logic shutdown the clock interface (processing block 1903). In one embodiment, theclock interface is implemented as a bubble generator first in first out(BGF) clock crossing buffer to enable interconnection between domains ofdifferent voltage and frequency, and it is shut down.

In one embodiment, once these operations have been completed, the agentfor the core sends an acknowledgement that this phase has beencompleted. In one embodiment, this acknowledgement is sent in parallelwith the acknowledgements that the other phases have been completed.

FIG. 20 is a flow diagram of one embodiment of a FSM process to stopclocking of the core. In one embodiment, the process is performed byprocessing logic that may comprise hardware (circuitry, dedicated logic,etc.), software (such as is run on a general purpose computer system ora dedicated machine), firmware, or a combination of the three.

Referring to FIG. 20, the process begins by processing logic asserting acore reset signal to reset the core (processing block 2001). Next,processing logic gates the clock to the core (processing block 2002) andturns off the clock generator (e.g., a PLL) (processing block 2003).Afterwards, processing logic switches a storage array (e.g., a coreSRAM, etc.) to a different power rail to enable the storage array tocontinue to receive power during the reduce power consumption state(processing block 2004). In one embodiment, the storage array stores thecore state after the core cache memories are flushed and the core'sclock has been turned off. In one embodiment, the storage arraycomprises a Last Level Cache (LLC). In one embodiment, the new powerrail is a lower voltage power rail that provides enough power to keepthe data in the storage array refreshed. The memory may also be placedinto a self-refresh mode. Lastly, processing logic removes voltage fromthe core (processing block 2005). In one embodiment, processing logicremoves the voltage from the core by turning off a switch than enablespower through to the core. In one embodiment, a power gate is used tocut off the voltage to the core.

In one embodiment, once these operations have been completed, the agentfor the core sends an acknowledgement that this phase has beencompleted. In one embodiment, this acknowledgement is sent in parallelwith the acknowledgements that the other phases have been completed.

Note that at this point the core is in an appropriate state to enableDVFS to cause a voltage and/or frequency transition for the core whilethe core is at a safe point. Therefore, at this point, the frequency andvoltage may be updated, and this may be performed by one or more otherFSMs.

FIG. 21 is a flow diagram of one embodiment of a FSM process to exit areduced power consumption state. In one embodiment, the process isperformed by processing logic that may comprise hardware (circuitry,dedicated logic, etc.), software (such as is run on a general purposecomputer system or a dedicated machine), firmware, or a combination ofthe three.

Referring to FIG. 21, the process begins by processing logic startingthe clock generator (processing block 2101). In one embodiment, startingthe clock generator comprises turning on a PLL. Next, processing logicapplies the voltage to the core (processing block 2102). In oneembodiment, to apply the voltage to the core, processing logic signals aswitch (e.g., a power gate) to enable the voltage to the core.Processing logic also brings the core voltage up to a specified level(processing block 2103). This voltage level may be the level specifiedby the PCU as part of frequency and voltage scaling. Once the voltagehas been brought up to the specified level, processing logic generatesan indication (e.g., asserts a pwrgood signal) indicating that the corehas power (processing block 2014). Processing logic also switches thecore memory array to the core power rail (processing block 2015) andsets the clock ratio for the clock generator and waits for the clockgenerator to be ready (processing block 2016). In one embodiment, theclock generator is a PLL and the ratio (e.g., 2 x for clock doubling, 3x for clock tripling, etc.) has been programmed, the PLL proceeds toachieve lock. The ratio may be set as part of dynamic frequency andvoltage scaling. When the PLL is locked, then the PLL is ready. Lastly,processing logic clears the core state (processing block 2017).

In one embodiment, once these operations have been completed, the agentfor the core sends an acknowledgement that this phase has beencompleted. In one embodiment, this acknowledgement is sent in parallelwith the acknowledgements that the other phases have been completed.

In one embodiment, if exiting other than the C-state C6, processingblocks 2014 and 2015 are skipped once the core voltage is brought up tothe specified level and the PLL is ready, the phase is completed. Forexample, if performing a dynamic voltage and frequency scalingoperation, the operations of sending an indication (e.g., a pwrgoodsignal) that the core has power and switching the memory array (e.g., anSRAM, LLC, etc.) to different a power rail other than the core's powerrail are not performed, and after the PLL is ready, the phase is done.

FIG. 22 is a flow diagram of one embodiment of a FSM process to causethe core to resume executing instructions. In one embodiment, theprocess is performed by processing logic that may comprise hardware(circuitry, dedicated logic, etc.), software (such as is run on ageneral purpose computer system or a dedicated machine), firmware, or acombination of the three.

Referring to FIG. 22, the process begins by processing logic load corewith different messages (processing block 2201). In one embodiment,these messages include an indication of the type of exit: 1) an exitfrom reset, 2) an exit from C6, etc. The messages can also indicate afrequency of operation for the core. This may be a new frequencyselected as part of DVFS. In one embodiment, the messages also specify aSoC fabric topology. Next, processing logic restarts the interconnectcommunications (processing block 2202). In one embodiment, thisprocessing logic unblocks the input/output (I/O) interface to the core.In one embodiment, the interface is the IDI. Once the interface is nolonger blocked, processing logic loads a boot vector that indicates amemory location of where the core state is saved to enable the core tocontinue processing where it left off (processing block 2203).

In one embodiment, once these operations have been completed, the agentfor the core sends an acknowledgement that this phase has beencompleted. In one embodiment, this acknowledgement is sent in parallelwith the acknowledgements that the other phases have been completed.

In one embodiment, the agent includes a scheduler that schedules thephases of the power control flow. In the case of the five phasesdepicted by the five FSMs described above, the scheduler schedules theoperations of the five phases. In one embodiment, this is done inresponse to requests from the PCU to perform the plurality of phases ofthe power control flow. After the phases have been completed, the agentssends acknowledgements indicating the plurality of phases have beencompleted. In one embodiment, the acknowledgements are sent together inparallel only after all of the plurality of phases have been completed.This may be accomplished by sending the acknowledgements in the samemessage.

Note that in one embodiment, all the phases may not be relevant to aparticular component. In such cases, the agent only performs therelevant phases. However, the agent still sends acknowledgementsindicating completion of all the phases even though some were notperformed. For example, when an agent for the memory controller isrequested by the PCU to perform the five stages (e.g., the five FSMs),there is no need to stop and drain the core. Therefore, this stage canbe skipped by the memory controller's agent. Even so, when the otherfour stages have been performed, the agent for the memory controllersends all five acknowledgements to the PCU.

There are a number of example embodiments described herein.

Example 1 is an integrated circuit that includes a plurality ofprocessing entities to execute operations, a power controller coupled tothe plurality of processing entities to control power management for theplurality of processing entities, and a plurality of agents, where eachof the plurality of agents is operable to perform a power control flowfor one of the processing entities by separately scheduling, using ascheduler, and executing a plurality of power control flow phases inresponse to the power controller requesting the plurality of powercontrol flow phases be performed, and each agent is operable to send aplurality of acknowledgements, one acknowledgement for each phase, uponcompletion of the plurality of power control flow phases.

Example 2 is the integrated circuit of example 1 that may optionallyinclude that the plurality of processing entities comprises at least onecore.

Example 3 is the integrated circuit of example 1 that may optionallyinclude that the plurality of processing entities comprises a memorycontroller.

Example 4 is the integrated circuit of example 1 that may optionallyinclude that each of the plurality of agents is operable to sendacknowledgements in parallel indicating phases of plurality of powercontrol flow phases have been completed only after all of the pluralityof power control flow phases have been completed.

Example 5 is the integrated circuit of example 1 that may optionallyinclude that at least one of the plurality of agents is operable to sendat least one of the acknowledgements indicating completion of one ormore of the plurality of phases that were not performed for itsassociated processing entity due to the one or more phases not beingrelevant to the processing entity.

Example 6 is the integrated circuit of example 1 that may optionallyinclude that each agent comprises circuitry to perform the power controlflow for its associated processing entity according to a plurality offinite state machines (FSMs), and each of the FSMs is operable tospecify operations for one phase of the power control flow, and furtherwherein each agent accesses the FSMs and schedules the operationsspecified by the FSMs in response to receiving the plurality of requestsfrom the PCU.

Example 7 is the integrated circuit of example 6 that may optionallyinclude that the plurality of FSMs set forth operations to transitionone of the processing entities into and out of a C6 power state.

Example 8 is the integrated circuit of example 6 that may optionallyinclude that the plurality of FSMs set forth operations to enable one ofthe processing entities to undergo voltage and frequency scaling.

Example 9 is the integrated circuit of example 6 that may optionallyinclude that the plurality of FSMs comprises: a first FSM to specifyoperations associated with placing the core in a quiesced state; asecond FSM to specify operations associated with blocking one or moreinterfaces to the core; a third FSM to specify operations associatedwith stopping core clocking; a fourth FSM to specify operationsassociated with exiting a reduced power consumption state in which thecore resides; and a fifth FSM to specify operations associated withcausing the core to resume executing instructions.

Example 10 is the integrated circuit of example 1 that may optionallyinclude that each of the plurality of agents is operable to perform thepower control flow in response to a plurality of requests sent within asingle message, each request of the plurality of requests for requestingperformance of one of the plurality of power control flow phases.

Example 11 is a processor that includes a plurality of cores to executeoperations and a memory controller, a power controller coupled to theplurality of processing entities to control power management for theplurality of processing entities; and a plurality of agents, each of theplurality of agents to perform power control flow for one of theplurality of cores and memory controller, where each agent comprises ascheduler operable to separately schedule a plurality of power controlflow phases in response to requesting from the power controller toperform the power control flow phases, and circuitry to perform aplurality of finite state machines (FSMs) that specify operations forthe power control flow for its associated processing entity, each of theplurality of FSMs to specify operations for one phase of the powercontrol flow, and further wherein each agent is operable to access theFSMs and use the scheduler to schedule operations specified by the FSMsin response to the requesting from the power controller, and each agentis operable to send a plurality of acknowledgements, one acknowledgementfor each phase, upon completion of the plurality of power control flowphases.

Example 12 is the processor of example 11 that may optionally includethat each of the plurality of agents is operable to sendacknowledgements in parallel indicating phases of plurality of powercontrol flow phases have been completed only after all of the pluralityof power control flow phases have been completed.

Example 13 is the processor of example 11 that may optionally includethat at least one of the plurality of agents is operable to send atleast one of the acknowledgements indicating completion of one or moreof the plurality of phases that were not performed for its associatedprocessing entity due to the one or more phases not being relevant tothe processing entity.

Example 14 is the processor of example 11 that may optionally includethat the plurality of FSMs set forth operations to transition one of theprocessing entities into and out of a C6 power state and to undergovoltage and frequency scaling.

Example 15 is a system that includes an interconnect; a dynamic randomaccess memory (DRAM) coupled to the interconnect; and a processorcoupled the interconnect, wherein the processor includes a plurality ofprocessing entities to execute operations, a power controller coupled tothe plurality of processing entities to control power management for theplurality of processing entities, and a plurality of agents, each of theplurality of agents to perform power control flow for one of theprocessing entities by separately scheduling, using a scheduler, andexecuting a plurality of power control flow phases in response to thepower controller requesting the plurality of power control flow phasesbe performed, where each agent is operable to send a plurality ofacknowledgements, one acknowledgement in each phase, upon completion ofthe plurality of power control flow phases.

Example 16 is the system of example 15 that may optionally include thatthe plurality of processing entities comprises at least one core.

Example 17 is the system of example 15 that may optionally include thatthe plurality of processing entities comprises a memory controller.

Example 18 is the system of example 15 that may optionally include thateach of the plurality of agents is operable to send acknowledgementsindicating phases of plurality of power control flow phases have beencompleted only after all of the plurality of power control flow phaseshave been completed.

Example 19 is the system of example 15 that may optionally include thatat least one of the plurality of agents is operable to send at least oneof the acknowledgements indicating completion of one or more of theplurality of phases that were not performed for its associatedprocessing entity due to the one or more phases not being relevant tothe processing entity.

Example 20 is the system of example 15 that may optionally include thateach agent comprises circuitry to perform the power control flow for itsassociated processing entity according to a plurality of finite statemachines (FSMs), each of the FSMs to specify operations for one phase ofthe power control flow, and further wherein each agent accesses the FSMsand schedules the operations specified by the FSMs in response toreceiving the plurality of requests from the power controller.

Example 21 is the system of example 15 that may optionally include thatthe plurality of FSMs comprises: a first FSM to specify operationsassociated with placing the core in a quiesced state; a second FSM tospecify operations associated with blocking one or more interfaces tothe core; a third FSM to specify operations associated with stoppingcore clocking; a fourth FSM to specify operations associated withexiting a reduced power consumption state in which the core resides; anda fifth FSM to specify operations associated with causing the core toresume executing instructions.

Example 22 is a method that includes a power controller requestingperformance of a power control flow with respect to a core of aprocessor; performing the power control flow for the core, includingseparately scheduling a plurality of power control flow phases inresponse to the power controller requesting the plurality of powercontrol flow phases be performed, and performing operations for each ofthe power control flow phases according to a finite state machine (FSM)associated with the phase, including accessing a plurality of FSMsoperable to specify operations for the power control flow for the core,each of the plurality of FSMs to specify operations for one phase of thepower control flow, and sending a plurality of acknowledgements, oneacknowledgement for each phase, upon completion of the plurality ofpower control flow phases.

Example 23 is the method of example 22 that may optionally includesending a plurality of acknowledgements comprises sendingacknowledgements in parallel indicating phases of plurality of powercontrol flow phases have been completed only after all of the pluralityof power control flow phases have been completed.

Example 24 is the method of example 22 that may optionally includesending a plurality of acknowledgements in parallel comprises indicatingcompletion of one or more of the plurality of phases that were notperformed for its associated processing entity due to the one or morephases not being relevant to the processing entity.

Example 25 is the method of example 22 that may optionally include thatthe plurality of FSMs set forth operations to transition one of theprocessing entities into and out of a C6 power state and to undergovoltage and frequency scaling.

Example 26 is the method of example 22 that may optionally include thatthe plurality of requests are sent in one message.

Example 27 is a machine-readable medium having stored thereon aninstruction, which if performed by a machine causes the machine toperform a method that includes a power controller requesting performanceof a power control flow with respect to a core of a processor;performing the power control flow for the core, including separatelyscheduling a plurality of power control flow phases in response to thepower controller requesting the plurality of power control flow phasesbe performed, and performing operations for each of the power controlflow phases according to a finite state machine (FSM) associated withthe phase, including accessing a plurality of FSMs operable to specifyoperations for the power control flow for the core, each of theplurality of FSMs to specify operations for one phase of the powercontrol flow, and sending a plurality of acknowledgements in parallel,one acknowledgement for each phase, upon completion of the plurality ofpower control flow phases.

Example 28 is the machine-readable medium of example 27 that mayoptionally include that the method includes sending a plurality ofacknowledgements in parallel comprises sending acknowledgementsindicating phases of plurality of power control flow phases have beencompleted only after all of the plurality of power control flow phaseshave been completed.

Example 29 is the machine-readable medium of example 27 that mayoptionally include that the method includes sending a plurality ofacknowledgements in parallel comprises indicating completion of one ormore of the plurality of phases that were not performed for itsassociated processing entity due to the one or more phases not beingrelevant to the processing entity.

Example 30 is a processor or other apparatus operative to perform themethod of any one of examples 22 to 26.

Example 31 is a processor or other apparatus that includes means forperforming the method of any one of examples 22 to 26.

Example 32 is a processor or other apparatus substantially as describedherein.

Example 33 is a processor or other apparatus that is operative toperform any method substantially as described herein.

Example 34 is a processor or other apparatus that is operative toperform any instructions/operations substantially as described herein.

Embodiments of the mechanisms disclosed herein may be implemented inhardware, software, firmware, or a combination of such implementationapproaches. Embodiments of the invention may be implemented as computerprograms or program code executing on programmable systems comprising atleast one processor, a storage system (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device.

Program code may be applied to input instructions to perform thefunctions described herein and generate output information. The outputinformation may be applied to one or more output devices, in knownfashion. For purposes of this application, a processing system includesany system that has a processor, such as, for example; a digital signalprocessor (DSP), a microcontroller, an application specific integratedcircuit (ASIC), or a microprocessor.

The program code may be implemented in a high level procedural or objectoriented programming language to communicate with a processing system.The program code may also be implemented in assembly or machinelanguage, if desired. In fact, the mechanisms described herein are notlimited in scope to any particular programming language. In any case,the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Such machine-readable storage media may include, without limitation,non-transitory, tangible arrangements of articles manufactured or formedby a machine or device, including storage media such as hard disks, anyother type of disk including floppy disks, optical disks, compact diskread-only memories (CD-ROMs), compact disk rewritable's (CD-RWs), andmagneto-optical disks, semiconductor devices such as read-only memories(ROMs), random access memories (RAMs) such as dynamic random accessmemories (DRAMs), static random access memories (SRAMs), erasableprogrammable read-only memories (EPROMs), flash memories, electricallyerasable programmable read-only memories (EEPROMs), magnetic or opticalcards, or any other type of media suitable for storing electronicinstructions.

Accordingly, embodiments of the invention also include non-transitory,tangible machine-readable media containing instructions or containingdesign data, such as Hardware Description Language (HDL), which definesstructures, circuits, apparatuses, processors and/or system featuresdescribed herein. Such embodiments may also be referred to as programproducts.

In some cases, an instruction converter may be used to convert aninstruction from a source instruction set to a target instruction set.For example, the instruction converter may translate (e.g., using staticbinary translation, dynamic binary translation including dynamiccompilation), morph, emulate, or otherwise convert an instruction to oneor more other instructions to be processed by the core. The instructionconverter may be implemented in software, hardware, firmware, or acombination thereof. The instruction converter may be on processor, offprocessor, or part on and part off processor.

Thus, techniques for performing one or more instructions according to atleast one embodiment are disclosed. While certain exemplary embodimentshave been described and shown in the accompanying drawings, it is to beunderstood that such embodiments are merely illustrative of and notrestrictive on the broad invention, and that this invention not belimited to the specific constructions and arrangements shown anddescribed, since various other modifications may occur to thoseordinarily skilled in the art upon studying this disclosure. In an areaof technology such as this, where growth is fast and furtheradvancements are not easily foreseen, the disclosed embodiments may bereadily modifiable in arrangement and detail as facilitated by enablingtechnological advancements without departing from the principles of thepresent disclosure or the scope of the accompanying claims.

What is claimed is:
 1. An integrated circuit comprising: a plurality ofprocessing entities to execute operations; a power controller coupled tothe plurality of processing entities to control power management for theplurality of processing entities; and a plurality of agents, each of theplurality of agents to perform a power control flow for one of theprocessing entities by separately scheduling, using a scheduler, andexecuting a plurality of power control flow phases in response to thepower controller requesting the plurality of power control flow phasesbe performed, said each agent operable to send a plurality ofacknowledgements, one acknowledgement for each phase, upon completion ofthe plurality of power control flow phases, wherein each agent comprisescircuitry to perform the power control flow for its associatedprocessing entity according to a plurality of finite state machines(FSMs), each of the FSMs to specify operations for one phase of thepower control flow, and further wherein each agent accesses the FSMs andschedules the operations specified by the FSMs in response to receivingthe plurality of requests from the power controller.
 2. The integratedcircuit defined in claim 1 wherein the plurality of processing entitiescomprises at least one core.
 3. The integrated circuit defined in claim1 wherein the plurality of processing entities comprises a memorycontroller.
 4. The integrated circuit defined in claim 1 wherein each ofthe plurality of agents is operable to send acknowledgements in parallelindicating phases of plurality of power control flow phases have beencompleted only after all of the plurality of power control flow phaseshave been completed.
 5. The integrated circuit defined in claim 1wherein at least one of the plurality of agents is operable to send atleast one of the acknowledgements indicating completion of one or moreof the plurality of phases that were not performed for its associatedprocessing entity due to the one or more phases not being relevant tothe processing entity.
 6. The integrated circuit defined in claim 1wherein the plurality of FSMs set forth operations to transition one ofthe processing entities into and out of a C6 power state.
 7. Theintegrated circuit defined in claim 1 wherein the plurality of FSMs setforth operations to enable one of the processing entities to undergovoltage and frequency scaling.
 8. The integrated circuit defined inclaim 1 wherein the plurality of FSMs comprises: a first FSM to specifyoperations associated with placing the core in a quiesced state; asecond FSM to specify operations associated with blocking one or moreinterfaces to the core; a third FSM to specify operations associatedwith stopping core clocking; a fourth FSM to specify operationsassociated with exiting a reduced power consumption state in which thecore resides; and a fifth FSM to specify operations associated withcausing the core to resume executing instructions.
 9. The integratedcircuit defined in claim 1 wherein each of the plurality of agents isoperable to perform the power control flow in response to a plurality ofrequests sent within a single message from the power controller, eachrequest of the plurality of requests for requesting performance of oneof the plurality of power control flow phases.
 10. A processorcomprising: a plurality of cores to execute operations and a memorycontroller; a power controller coupled to the plurality of processingentities, including a plurality of core and a memory controller tocontrol power management for the plurality of processing entities; and aplurality of agents, each of the plurality of agents to perform a powercontrol flow for one of the plurality of cores and the memorycontroller, each agent comprising a scheduler operable to separatelyschedule a plurality of power control flow phases in response torequesting from the power controller to perform the power control flowphases, and circuitry to perform a plurality of finite state machines(FSMs) that specify operations for the power control flow for itsassociated processing entity, each of the plurality of FSMs to specifyoperations for one phase of the power control flow, and further whereineach agent is operable to access the FSMs and use the scheduler toschedule operations specified by the FSMs in response to the requestingfrom the power controller, and said each agent operable to send aplurality of acknowledgements, one acknowledgement for each phase, uponcompletion of the plurality of power control flow phases.
 11. Theprocessor defined in claim 10 wherein each of the plurality of agents isoperable to send acknowledgements in parallel indicating phases ofplurality of power control flow phases have been completed only afterall of the plurality of power control flow phases have been completed.12. The processor defined in claim 10 wherein at least one of theplurality of agents is operable to send at least one of theacknowledgements indicating completion of one or more of the pluralityof phases that were not performed for its associated processing entitydue to the one or more phases not being relevant to the processingentity.
 13. The processor defined in claim 10 wherein the plurality ofFSMs set forth operations to transition one of the processing entitiesinto and out of a C6 power state and to undergo voltage and frequencyscaling.
 14. A system comprising: an interconnect; a dynamic randomaccess memory (DRAM) coupled to the interconnect; and a processorcoupled the interconnect, including a plurality of processing entitiesto execute operations, a power controller coupled to the plurality ofprocessing entities to control power management for the plurality ofprocessing entities, and a plurality of agents, each of the plurality ofagents to perform a power control flow for one of the processingentities by separately scheduling, using a scheduler, and executing aplurality of power control flow phases in response to the powercontroller requesting the plurality of power control flow phases beperformed, said each agent operable to send a plurality ofacknowledgements, one acknowledgement in each phase, upon completion ofthe plurality of power control flow phases, wherein each agent comprisescircuitry to perform the power control flow for its associatedprocessing entity according to a plurality of finite state machines(FSMs), each of the FSMs to specify operations for one phase of thepower control flow, and further wherein each agent accesses the FSMs andschedules the operations specified by the FSMs in response to receivingthe plurality of requests from the power controller.
 15. The systemdefined in claim 14 wherein the plurality of processing entitiescomprises at least one core.
 16. The system defined in claim 14 whereineach of the plurality of agents is operable to send acknowledgementsindicating phases of plurality of power control flow phases have beencompleted only after all of the plurality of power control flow phaseshave been completed.
 17. The system defined in claim 14 wherein at leastone of the plurality of agents is operable to send at least one of theacknowledgements indicating completion of one or more of the pluralityof phases that were not performed for its associated processing entitydue to the one or more phases not being relevant to the processingentity.
 18. The system defined in claim 14 wherein the plurality of FSMscomprises: a first FSM to specify operations associated with placing thecore in a quiesced state; a second FSM to specify operations associatedwith blocking one or more interfaces to the core; a third FSM to specifyoperations associated with stopping core clocking; a fourth FSM tospecify operations associated with exiting a reduced power consumptionstate in which the core resides; and a fifth FSM to specify operationsassociated with causing the core to resume executing instructions.
 19. Amethod comprising: a power controller requesting performance of a powercontrol flow with respect to a core of a processor; performing the powercontrol flow for the core, including separately scheduling a pluralityof power control flow phases in response to the power controllerrequesting the plurality of power control flow phases be performed, andperforming operations for each of the power control flow phasesaccording to a finite state machine (FSM) associated with the phase,including accessing a plurality of FSMs operable to specify operationsfor the power control flow for the core, each of the plurality of FSMsto specify operations for one phase of the power control flow, andsending a plurality of acknowledgements, one acknowledgement for eachphase, upon completion of the plurality of power control flow phases.20. The method defined in claim 19 wherein sending a plurality ofacknowledgements comprises sending acknowledgements in parallelindicating phases of plurality of power control flow phases have beencompleted only after all of the plurality of power control flow phaseshave been completed.
 21. A non-transitory machine-readable medium havingstored thereon an instruction, which if performed by a machine causesthe machine to perform a method comprising: a power controllerrequesting performance of a power control flow with respect to a core ofa processor; performing the power control flow for the core, includingseparately scheduling a plurality of power control flow phases inresponse to the power controller requesting the plurality of powercontrol flow phases be performed, and performing operations for each ofthe power control flow phases according to a finite state machine (FSM)associated with the phase, including accessing a plurality of FSMsoperable to specify operations for the power control flow for the core,each of the plurality of FSMs to specify operations for one phase of thepower control flow, and sending a plurality of acknowledgements inparallel, one acknowledgement for each phase, upon completion of theplurality of power control flow phases.
 22. The non-transitorymachine-readable medium defined in claim 21 wherein sending a pluralityof acknowledgements in parallel comprises sending acknowledgementsindicating phases of plurality of power control flow phases have beencompleted only after all of the plurality of power control flow phaseshave been completed.
 23. The non-transitory machine-readable mediumdefined in claim 21 wherein sending a plurality of acknowledgements inparallel comprises indicating completion of one or more of the pluralityof phases that were not performed for its associated processing entitydue to the one or more phases not being relevant to the processingentity.